gstreamer/subprojects/gst-plugins-good/sys/v4l2/gstv4l2videoenc.c

/*
 * Copyright (C) 2014-2017 SUMOMO Computer Association
 *     Authors Ayaka <ayaka@soulik.info>
 * Copyright (C) 2017 Collabora Ltd.
 *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#include "gstv4l2object.h"
#include "gstv4l2videoenc.h"

#include <string.h>
#include <glib/gi18n-lib.h>

GST_DEBUG_CATEGORY_STATIC (gst_v4l2_video_enc_debug);
#define GST_CAT_DEFAULT gst_v4l2_video_enc_debug

typedef struct
{
  gchar *device;
  GstCaps *sink_caps;
  GstCaps *src_caps;
  const GstV4l2Codec *codec;
} GstV4l2VideoEncCData;

enum
{
  PROP_0,
  V4L2_STD_OBJECT_PROPS,
};

#define gst_v4l2_video_enc_parent_class parent_class
G_DEFINE_ABSTRACT_TYPE (GstV4l2VideoEnc, gst_v4l2_video_enc,
    GST_TYPE_VIDEO_ENCODER);

static void
gst_v4l2_video_enc_set_property (GObject * object,
    guint prop_id, const GValue * value, GParamSpec * pspec)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (object);

  switch (prop_id) {
    case PROP_CAPTURE_IO_MODE:
      if (!gst_v4l2_object_set_property_helper (self->v4l2capture,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;

      /* By default, only set on output */
    default:
      if (!gst_v4l2_object_set_property_helper (self->v4l2output,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;
  }
}

static void
gst_v4l2_video_enc_get_property (GObject * object,
    guint prop_id, GValue * value, GParamSpec * pspec)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (object);

  switch (prop_id) {
    case PROP_CAPTURE_IO_MODE:
      if (!gst_v4l2_object_get_property_helper (self->v4l2capture,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;

      /* By default read from output */
    default:
      if (!gst_v4l2_object_get_property_helper (self->v4l2output,
              prop_id, value, pspec)) {
        G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      }
      break;
  }
}

static gboolean
gst_v4l2_video_enc_open (GstVideoEncoder * encoder)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  GstV4l2Error error = GST_V4L2_ERROR_INIT;
  GstCaps *codec_caps;

  GST_DEBUG_OBJECT (self, "Opening");

  if (!gst_v4l2_object_open (self->v4l2output, &error))
    goto failure;

  if (!gst_v4l2_object_open_shared (self->v4l2capture, self->v4l2output))
    goto failure;

  self->probed_sinkcaps = gst_v4l2_object_probe_caps (self->v4l2output,
      gst_v4l2_object_get_raw_caps ());

  if (gst_caps_is_empty (self->probed_sinkcaps))
    goto no_raw_format;

  codec_caps = gst_pad_get_pad_template_caps (encoder->srcpad);
  self->probed_srccaps = gst_v4l2_object_probe_caps (self->v4l2capture,
      codec_caps);
  gst_caps_unref (codec_caps);

  if (gst_caps_is_empty (self->probed_srccaps))
    goto no_encoded_format;

  return TRUE;

no_encoded_format:
  GST_ELEMENT_ERROR (self, RESOURCE, SETTINGS,
      (_("Encoder on device %s has no supported output format"),
          self->v4l2output->videodev), (NULL));
  goto failure;


no_raw_format:
  GST_ELEMENT_ERROR (self, RESOURCE, SETTINGS,
      (_("Encoder on device %s has no supported input format"),
          self->v4l2output->videodev), (NULL));
  goto failure;

failure:
  if (GST_V4L2_IS_OPEN (self->v4l2output))
    gst_v4l2_object_close (self->v4l2output);

  if (GST_V4L2_IS_OPEN (self->v4l2capture))
    gst_v4l2_object_close (self->v4l2capture);

  gst_caps_replace (&self->probed_srccaps, NULL);
  gst_caps_replace (&self->probed_sinkcaps, NULL);

  gst_v4l2_error (self, &error);

  return FALSE;
}

static gboolean
gst_v4l2_video_enc_close (GstVideoEncoder * encoder)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);

  GST_DEBUG_OBJECT (self, "Closing");

  gst_v4l2_object_close (self->v4l2output);
  gst_v4l2_object_close (self->v4l2capture);
  gst_caps_replace (&self->probed_srccaps, NULL);
  gst_caps_replace (&self->probed_sinkcaps, NULL);

  return TRUE;
}

static gboolean
gst_v4l2_video_enc_start (GstVideoEncoder * encoder)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);

  GST_DEBUG_OBJECT (self, "Starting");

  gst_v4l2_object_unlock (self->v4l2output);
  g_atomic_int_set (&self->active, TRUE);
  self->output_flow = GST_FLOW_OK;

  return TRUE;
}

static gboolean
gst_v4l2_video_enc_stop (GstVideoEncoder * encoder)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);

  GST_DEBUG_OBJECT (self, "Stopping");

  gst_v4l2_object_unlock (self->v4l2output);
  gst_v4l2_object_unlock (self->v4l2capture);

  /* Wait for capture thread to stop */
  gst_pad_stop_task (encoder->srcpad);

  GST_VIDEO_ENCODER_STREAM_LOCK (encoder);
  self->output_flow = GST_FLOW_OK;
  GST_VIDEO_ENCODER_STREAM_UNLOCK (encoder);

  /* Should have been flushed already */
  g_assert (g_atomic_int_get (&self->active) == FALSE);
  g_assert (g_atomic_int_get (&self->processing) == FALSE);

  gst_v4l2_object_stop (self->v4l2output);
  gst_v4l2_object_stop (self->v4l2capture);

  if (self->input_state) {
    gst_video_codec_state_unref (self->input_state);
    self->input_state = NULL;
  }

  GST_DEBUG_OBJECT (self, "Stopped");

  return TRUE;
}

static gboolean
gst_v4l2_encoder_cmd (GstV4l2Object * v4l2object, guint cmd, guint flags)
{
  struct v4l2_encoder_cmd ecmd = { 0, };

  GST_DEBUG_OBJECT (v4l2object->element,
      "sending v4l2 encoder command %u with flags %u", cmd, flags);

  if (!GST_V4L2_IS_OPEN (v4l2object))
    return FALSE;

  ecmd.cmd = cmd;
  ecmd.flags = flags;
  if (v4l2object->ioctl (v4l2object->video_fd, VIDIOC_ENCODER_CMD, &ecmd) < 0)
    goto ecmd_failed;

  return TRUE;

ecmd_failed:
  if (errno == ENOTTY) {
    GST_INFO_OBJECT (v4l2object->element,
        "Failed to send encoder command %u with flags %u for '%s'. (%s)",
        cmd, flags, v4l2object->videodev, g_strerror (errno));
  } else {
    GST_ERROR_OBJECT (v4l2object->element,
        "Failed to send encoder command %u with flags %u for '%s'. (%s)",
        cmd, flags, v4l2object->videodev, g_strerror (errno));
  }
  return FALSE;
}

static GstFlowReturn
gst_v4l2_video_enc_finish (GstVideoEncoder * encoder)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  GstFlowReturn ret = GST_FLOW_OK;

  if (gst_pad_get_task_state (encoder->srcpad) != GST_TASK_STARTED)
    goto done;

  GST_DEBUG_OBJECT (self, "Finishing encoding");

  /* drop the stream lock while draining, so remaining buffers can be
   * pushed from the src pad task thread */
  GST_VIDEO_ENCODER_STREAM_UNLOCK (encoder);

  if (gst_v4l2_encoder_cmd (self->v4l2capture, V4L2_ENC_CMD_STOP, 0)) {
    GstTask *task = encoder->srcpad->task;

    /* Wait for the task to be drained */
    GST_DEBUG_OBJECT (self, "Waiting for encoder stop");
    GST_OBJECT_LOCK (task);
    while (GST_TASK_STATE (task) == GST_TASK_STARTED)
      GST_TASK_WAIT (task);
    GST_OBJECT_UNLOCK (task);
    ret = GST_FLOW_FLUSHING;
  }

  /* and ensure the processing thread has stopped in case another error
   * occurred. */
  gst_v4l2_object_unlock (self->v4l2capture);
  gst_pad_stop_task (encoder->srcpad);
  GST_VIDEO_ENCODER_STREAM_LOCK (encoder);

  if (ret == GST_FLOW_FLUSHING)
    ret = self->output_flow;

  GST_DEBUG_OBJECT (encoder, "Done draining buffers");

done:
  return ret;
}

static gboolean
gst_v4l2_video_enc_set_format (GstVideoEncoder * encoder,
    GstVideoCodecState * state)
{
  gboolean ret = TRUE;
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  GstV4l2Error error = GST_V4L2_ERROR_INIT;
  GstCaps *outcaps;
  GstVideoCodecState *output;

  GST_DEBUG_OBJECT (self, "Setting format: %" GST_PTR_FORMAT, state->caps);

  if (self->input_state) {
    if (gst_v4l2_object_caps_equal (self->v4l2output, state->caps)) {
      GST_DEBUG_OBJECT (self, "Compatible caps");
      return TRUE;
    }

    if (gst_v4l2_video_enc_finish (encoder) != GST_FLOW_OK)
      return FALSE;

    gst_v4l2_object_stop (self->v4l2output);
    gst_v4l2_object_stop (self->v4l2capture);

    gst_video_codec_state_unref (self->input_state);
    self->input_state = NULL;
  }

  outcaps = gst_pad_get_pad_template_caps (encoder->srcpad);
  outcaps = gst_caps_make_writable (outcaps);
  output = gst_video_encoder_set_output_state (encoder, outcaps, state);
  gst_video_codec_state_unref (output);

  if (!gst_video_encoder_negotiate (encoder))
    return FALSE;

  if (!gst_v4l2_object_set_format (self->v4l2output, state->caps, &error)) {
    gst_v4l2_error (self, &error);
    return FALSE;
  }

  self->input_state = gst_video_codec_state_ref (state);

  GST_DEBUG_OBJECT (self, "output caps: %" GST_PTR_FORMAT, state->caps);

  return ret;
}

static gboolean
gst_v4l2_video_enc_flush (GstVideoEncoder * encoder)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);

  GST_DEBUG_OBJECT (self, "Flushing");

  /* Ensure the processing thread has stopped for the reverse playback
   * iscount case */
  if (g_atomic_int_get (&self->processing)) {
    GST_VIDEO_ENCODER_STREAM_UNLOCK (encoder);

    gst_v4l2_object_unlock_stop (self->v4l2output);
    gst_v4l2_object_unlock_stop (self->v4l2capture);
    gst_pad_stop_task (encoder->srcpad);

    GST_VIDEO_ENCODER_STREAM_UNLOCK (encoder);

  }

  self->output_flow = GST_FLOW_OK;

  gst_v4l2_object_unlock_stop (self->v4l2output);
  gst_v4l2_object_unlock_stop (self->v4l2capture);

  return TRUE;
}

struct ProfileLevelCtx
{
  GstV4l2VideoEnc *self;
  const gchar *profile;
  const gchar *level;
};

static gboolean
get_string_list (GstStructure * s, const gchar * field, GQueue * queue)
{
  const GValue *value;

  value = gst_structure_get_value (s, field);

  if (!value)
    return FALSE;

  if (GST_VALUE_HOLDS_LIST (value)) {
    guint i;

    if (gst_value_list_get_size (value) == 0)
      return FALSE;

    for (i = 0; i < gst_value_list_get_size (value); i++) {
      const GValue *item = gst_value_list_get_value (value, i);

      if (G_VALUE_HOLDS_STRING (item))
        g_queue_push_tail (queue, g_value_dup_string (item));
    }
  } else if (G_VALUE_HOLDS_STRING (value)) {
    g_queue_push_tail (queue, g_value_dup_string (value));
  }

  return TRUE;
}

static gboolean
negotiate_profile_and_level (GstCapsFeatures * features, GstStructure * s,
    gpointer user_data)
{
  struct ProfileLevelCtx *ctx = user_data;
  GstV4l2VideoEncClass *klass = GST_V4L2_VIDEO_ENC_GET_CLASS (ctx->self);
  GstV4l2Object *v4l2object = GST_V4L2_VIDEO_ENC (ctx->self)->v4l2output;
  GQueue profiles = G_QUEUE_INIT;
  GQueue levels = G_QUEUE_INIT;
  gboolean failed = FALSE;
  const GstV4l2Codec *codec = klass->codec;

  if (codec->profile_cid && get_string_list (s, "profile", &profiles)) {
    GList *l;

    for (l = profiles.head; l; l = l->next) {
      struct v4l2_control control = { 0, };
      gint v4l2_profile;
      const gchar *profile = l->data;

      GST_TRACE_OBJECT (ctx->self, "Trying profile %s", profile);

      control.id = codec->profile_cid;

      control.value = v4l2_profile = codec->profile_from_string (profile);

      if (control.value < 0)
        continue;

      if (v4l2object->ioctl (v4l2object->video_fd, VIDIOC_S_CTRL, &control) < 0) {
        GST_WARNING_OBJECT (ctx->self, "Failed to set %s profile: '%s'",
            klass->codec_name, g_strerror (errno));
        break;
      }

      profile = codec->profile_to_string (control.value);

      if (control.value == v4l2_profile) {
        ctx->profile = profile;
        break;
      }

      if (g_list_find_custom (l, profile, g_str_equal)) {
        ctx->profile = profile;
        break;
      }
    }

    if (profiles.length && !ctx->profile)
      failed = TRUE;

    g_queue_foreach (&profiles, (GFunc) g_free, NULL);
    g_queue_clear (&profiles);
  }

  if (!failed && codec->level_cid && get_string_list (s, "level", &levels)) {
    GList *l;

    for (l = levels.head; l; l = l->next) {
      struct v4l2_control control = { 0, };
      gint v4l2_level;
      const gchar *level = l->data;

      GST_TRACE_OBJECT (ctx->self, "Trying level %s", level);

      control.id = codec->level_cid;
      control.value = v4l2_level = codec->level_from_string (level);

      if (control.value < 0)
        continue;

      if (v4l2object->ioctl (v4l2object->video_fd, VIDIOC_S_CTRL, &control) < 0) {
        GST_WARNING_OBJECT (ctx->self, "Failed to set %s level: '%s'",
            klass->codec_name, g_strerror (errno));
        break;
      }

      level = codec->level_to_string (control.value);

      if (control.value == v4l2_level) {
        ctx->level = level;
        break;
      }

      if (g_list_find_custom (l, level, g_str_equal)) {
        ctx->level = level;
        break;
      }
    }

    if (levels.length && !ctx->level)
      failed = TRUE;

    g_queue_foreach (&levels, (GFunc) g_free, NULL);
    g_queue_clear (&levels);
  }

  /* If it failed, we continue */
  return failed;
}

static gboolean
gst_v4l2_video_enc_negotiate (GstVideoEncoder * encoder)
{
  GstV4l2VideoEncClass *klass = GST_V4L2_VIDEO_ENC_GET_CLASS (encoder);
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  GstV4l2Object *v4l2object = self->v4l2output;
  GstCaps *allowed_caps;
  struct ProfileLevelCtx ctx = { self, NULL, NULL };
  GstVideoCodecState *state;
  GstStructure *s;
  const GstV4l2Codec *codec = klass->codec;

  GST_DEBUG_OBJECT (self, "Negotiating %s profile and level.",
      klass->codec_name);

  /* Only renegotiate on upstream changes */
  if (self->input_state)
    return TRUE;

  if (!codec)
    goto done;

  allowed_caps = gst_pad_get_allowed_caps (GST_VIDEO_ENCODER_SRC_PAD (encoder));

  if (allowed_caps) {

    if (gst_caps_is_empty (allowed_caps))
      goto not_negotiated;

    allowed_caps = gst_caps_make_writable (allowed_caps);

    /* negotiate_profile_and_level() will return TRUE on failure to keep
     * iterating, if gst_caps_foreach() returns TRUE it means there was no
     * compatible profile and level in any of the structure */
    if (gst_caps_foreach (allowed_caps, negotiate_profile_and_level, &ctx)) {
      goto no_profile_level;
    }

    gst_caps_unref (allowed_caps);
    allowed_caps = NULL;
  }

  if (codec->profile_cid && !ctx.profile) {
    struct v4l2_control control = { 0, };

    control.id = codec->profile_cid;

    if (v4l2object->ioctl (v4l2object->video_fd, VIDIOC_G_CTRL, &control) < 0)
      goto g_ctrl_failed;

    ctx.profile = codec->profile_to_string (control.value);
  }

  if (codec->level_cid && !ctx.level) {
    struct v4l2_control control = { 0, };

    control.id = codec->level_cid;

    if (v4l2object->ioctl (v4l2object->video_fd, VIDIOC_G_CTRL, &control) < 0)
      goto g_ctrl_failed;

    ctx.level = codec->level_to_string (control.value);
  }

  GST_DEBUG_OBJECT (self, "Selected %s profile %s at level %s",
      klass->codec_name, ctx.profile, ctx.level);

  state = gst_video_encoder_get_output_state (encoder);
  s = gst_caps_get_structure (state->caps, 0);

  if (codec->profile_cid)
    gst_structure_set (s, "profile", G_TYPE_STRING, ctx.profile, NULL);

  if (codec->level_cid)
    gst_structure_set (s, "level", G_TYPE_STRING, ctx.level, NULL);

done:
  if (!GST_VIDEO_ENCODER_CLASS (parent_class)->negotiate (encoder))
    return FALSE;

  return TRUE;

g_ctrl_failed:
  GST_WARNING_OBJECT (self, "Failed to get %s profile and level: '%s'",
      klass->codec_name, g_strerror (errno));
  goto not_negotiated;

no_profile_level:
  GST_WARNING_OBJECT (self, "No compatible level and profile in caps: %"
      GST_PTR_FORMAT, allowed_caps);
  goto not_negotiated;

not_negotiated:
  if (allowed_caps)
    gst_caps_unref (allowed_caps);
  return FALSE;
}

static gboolean
check_system_frame_number_too_old (guint32 current, guint32 old)
{
  guint32 absdiff = current > old ? current - old : old - current;

  /* More than 100 frames in the past, or current wrapped around */
  if (absdiff > 100) {
    /* Wraparound and difference is actually smaller than 100 */
    if (absdiff > G_MAXUINT32 - 100)
      return FALSE;
    return TRUE;
  }

  return FALSE;
}

static void
gst_v4l2_video_enc_loop (GstVideoEncoder * encoder)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  GstVideoCodecFrame *frame;
  GstBuffer *buffer = NULL;
  GstFlowReturn ret;

  GST_LOG_OBJECT (encoder, "Allocate output buffer");

  buffer = gst_video_encoder_allocate_output_buffer (encoder,
      self->v4l2capture->info.size);

  if (NULL == buffer) {
    ret = GST_FLOW_FLUSHING;
    goto beach;
  }

  /* FIXME Check if buffer isn't the last one here */

  GST_LOG_OBJECT (encoder, "Process output buffer");
  ret =
      gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL
      (self->v4l2capture->pool), &buffer, NULL);

  if (ret != GST_FLOW_OK)
    goto beach;

  if (GST_BUFFER_TIMESTAMP (buffer) % GST_SECOND != 0)
    GST_ERROR_OBJECT (encoder,
        "Driver bug detected - check driver with v4l2-compliance from http://git.linuxtv.org/v4l-utils.git");
  GST_LOG_OBJECT (encoder, "Got buffer for frame number %u",
      (guint32) (GST_BUFFER_PTS (buffer) / GST_SECOND));
  frame =
      gst_video_encoder_get_frame (encoder,
      GST_BUFFER_TIMESTAMP (buffer) / GST_SECOND);

  if (frame) {
    GstVideoCodecFrame *oldest_frame;
    gboolean warned = FALSE;

    /* Garbage collect old frames in case of codec bugs */
    while ((oldest_frame = gst_video_encoder_get_oldest_frame (encoder)) &&
        check_system_frame_number_too_old (frame->system_frame_number,
            oldest_frame->system_frame_number)) {
      gst_video_encoder_finish_frame (encoder, oldest_frame);
      oldest_frame = NULL;

      if (!warned) {
        g_warning ("%s: Too old frames, bug in encoder -- please file a bug",
            GST_ELEMENT_NAME (encoder));
        warned = TRUE;
      }
    }
    if (oldest_frame)
      gst_video_codec_frame_unref (oldest_frame);

    /* At this point, the delta unit buffer flag is already correctly set by
     * gst_v4l2_buffer_pool_process. Since gst_video_encoder_finish_frame
     * will overwrite it from GST_VIDEO_CODEC_FRAME_IS_SYNC_POINT (frame),
     * set that here.
     */
    if (GST_BUFFER_FLAG_IS_SET (buffer, GST_BUFFER_FLAG_DELTA_UNIT))
      GST_VIDEO_CODEC_FRAME_UNSET_SYNC_POINT (frame);
    else
      GST_VIDEO_CODEC_FRAME_SET_SYNC_POINT (frame);
    frame->output_buffer = buffer;
    buffer = NULL;
    ret = gst_video_encoder_finish_frame (encoder, frame);

    if (ret != GST_FLOW_OK)
      goto beach;
  } else {
    GST_WARNING_OBJECT (encoder, "Encoder is producing too many buffers");
    gst_buffer_unref (buffer);
  }

  return;

beach:
  GST_DEBUG_OBJECT (encoder, "Leaving output thread");

  gst_buffer_replace (&buffer, NULL);
  self->output_flow = ret;
  g_atomic_int_set (&self->processing, FALSE);
  gst_v4l2_object_unlock (self->v4l2output);
  gst_pad_pause_task (encoder->srcpad);
}

static void
gst_v4l2_video_enc_loop_stopped (GstV4l2VideoEnc * self)
{
  if (g_atomic_int_get (&self->processing)) {
    GST_DEBUG_OBJECT (self, "Early stop of encoding thread");
    self->output_flow = GST_FLOW_FLUSHING;
    g_atomic_int_set (&self->processing, FALSE);
  }

  GST_DEBUG_OBJECT (self, "Encoding task destroyed: %s",
      gst_flow_get_name (self->output_flow));

}

static GstFlowReturn
gst_v4l2_video_enc_handle_frame (GstVideoEncoder * encoder,
    GstVideoCodecFrame * frame)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  GstFlowReturn ret = GST_FLOW_OK;
  GstTaskState task_state;

  GST_DEBUG_OBJECT (self, "Handling frame %d", frame->system_frame_number);

  if (G_UNLIKELY (!g_atomic_int_get (&self->active)))
    goto flushing;

  task_state = gst_pad_get_task_state (GST_VIDEO_ENCODER_SRC_PAD (self));
  if (task_state == GST_TASK_STOPPED || task_state == GST_TASK_PAUSED) {
    GstBufferPool *pool = GST_BUFFER_POOL (self->v4l2output->pool);

    /* It is possible that the processing thread stopped due to an error or
     * when the last buffer has been met during the draining process. */
    if (self->output_flow != GST_FLOW_OK &&
        self->output_flow != GST_FLOW_FLUSHING &&
        self->output_flow != GST_V4L2_FLOW_LAST_BUFFER) {
      GST_DEBUG_OBJECT (self, "Processing loop stopped with error: %s, leaving",
          gst_flow_get_name (self->output_flow));
      ret = self->output_flow;
      goto drop;
    }

    /* Ensure input internal pool is active */
    if (!gst_buffer_pool_is_active (pool)) {
      GstStructure *config = gst_buffer_pool_get_config (pool);
      guint min = MAX (self->v4l2output->min_buffers,
          GST_V4L2_MIN_BUFFERS (self->v4l2output));

      gst_buffer_pool_config_set_params (config, self->input_state->caps,
          self->v4l2output->info.size, min, min);

      /* There is no reason to refuse this config */
      if (!gst_buffer_pool_set_config (pool, config))
        goto activate_failed;

      if (!gst_buffer_pool_set_active (pool, TRUE))
        goto activate_failed;
    }

    if (!gst_buffer_pool_set_active
        (GST_BUFFER_POOL (self->v4l2capture->pool), TRUE)) {
      GST_WARNING_OBJECT (self, "Could not activate capture buffer pool.");
      goto activate_failed;
    }

    GST_DEBUG_OBJECT (self, "Starting encoding thread");

    /* Start the processing task, when it quits, the task will disable input
     * processing to unlock input if draining, or prevent potential block */
    if (!gst_pad_start_task (encoder->srcpad,
            (GstTaskFunction) gst_v4l2_video_enc_loop, self,
            (GDestroyNotify) gst_v4l2_video_enc_loop_stopped))
      goto start_task_failed;
  }

  if (frame->input_buffer) {
    GST_VIDEO_ENCODER_STREAM_UNLOCK (encoder);
    GST_LOG_OBJECT (encoder, "Passing buffer with frame number %u",
        frame->system_frame_number);
    ret =
        gst_v4l2_buffer_pool_process (GST_V4L2_BUFFER_POOL (self->
            v4l2output->pool), &frame->input_buffer,
        &frame->system_frame_number);
    GST_VIDEO_ENCODER_STREAM_LOCK (encoder);

    if (ret == GST_FLOW_FLUSHING) {
      if (gst_pad_get_task_state (encoder->srcpad) != GST_TASK_STARTED)
        ret = self->output_flow;
      goto drop;
    } else if (ret != GST_FLOW_OK) {
      goto process_failed;
    }
  }

  gst_video_codec_frame_unref (frame);
  return ret;

  /* ERRORS */
activate_failed:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, SETTINGS,
        (_("Failed to allocate required memory.")),
        ("Buffer pool activation failed"));
    return GST_FLOW_ERROR;

  }
flushing:
  {
    ret = GST_FLOW_FLUSHING;
    goto drop;
  }
start_task_failed:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, FAILED,
        (_("Failed to start encoding thread.")), (NULL));
    g_atomic_int_set (&self->processing, FALSE);
    ret = GST_FLOW_ERROR;
    goto drop;
  }
process_failed:
  {
    GST_ELEMENT_ERROR (self, RESOURCE, FAILED,
        (_("Failed to process frame.")),
        ("Maybe be due to not enough memory or failing driver"));
    ret = GST_FLOW_ERROR;
    goto drop;
  }
drop:
  {
    gst_video_encoder_finish_frame (encoder, frame);
    return ret;
  }
}

static gboolean
gst_v4l2_video_enc_decide_allocation (GstVideoEncoder *
    encoder, GstQuery * query)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  GstVideoCodecState *state = gst_video_encoder_get_output_state (encoder);
  GstCaps *caps;
  GstV4l2Error error = GST_V4L2_ERROR_INIT;
  GstClockTime latency;
  gboolean ret = FALSE;

  /* We need to set the format here, since this is called right after
   * GstVideoEncoder have set the width, height and framerate into the state
   * caps. These are needed by the driver to calculate the buffer size and to
   * implement bitrate adaptation. */
  caps = gst_caps_copy (state->caps);
  gst_structure_remove_field (gst_caps_get_structure (caps, 0), "colorimetry");
  if (!gst_v4l2_object_set_format (self->v4l2capture, caps, &error)) {
    gst_v4l2_error (self, &error);
    gst_caps_unref (caps);
    ret = FALSE;
    goto done;
  }
  gst_caps_unref (caps);

  if (gst_v4l2_object_decide_allocation (self->v4l2capture, query)) {
    GstVideoEncoderClass *enc_class = GST_VIDEO_ENCODER_CLASS (parent_class);
    ret = enc_class->decide_allocation (encoder, query);
  }

  /* FIXME This may not be entirely correct, as encoder may keep some
   * observation without delaying the encoding. Linux Media API need some
   * more work to explicitly expressed the decoder / encoder latency. This
   * value will then become max latency, and the reported driver latency would
   * become the min latency. */
  if (!GST_CLOCK_TIME_IS_VALID (self->v4l2capture->duration))
    self->v4l2capture->duration = gst_util_uint64_scale_int (GST_SECOND, 1, 25);
  latency = self->v4l2capture->min_buffers * self->v4l2capture->duration;
  gst_video_encoder_set_latency (encoder, latency, latency);
  GST_DEBUG_OBJECT (self, "Setting latency: %" GST_TIME_FORMAT,
      GST_TIME_ARGS (latency));

done:
  gst_video_codec_state_unref (state);
  return ret;
}

static gboolean
gst_v4l2_video_enc_propose_allocation (GstVideoEncoder *
    encoder, GstQuery * query)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  gboolean ret = FALSE;

  GST_DEBUG_OBJECT (self, "called");

  if (query == NULL)
    ret = TRUE;
  else
    ret = gst_v4l2_object_propose_allocation (self->v4l2output, query);

  if (ret)
    ret = GST_VIDEO_ENCODER_CLASS (parent_class)->propose_allocation (encoder,
        query);

  return ret;
}

static gboolean
gst_v4l2_video_enc_src_query (GstVideoEncoder * encoder, GstQuery * query)
{
  gboolean ret = TRUE;
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_CAPS:{
      GstCaps *filter, *result = NULL;
      GstPad *pad = GST_VIDEO_ENCODER_SRC_PAD (encoder);

      gst_query_parse_caps (query, &filter);

      /* FIXME Try and not probe the entire encoder, but only the implement
       * subclass format */
      if (self->probed_srccaps) {
        GstCaps *tmpl = gst_pad_get_pad_template_caps (pad);
        result = gst_caps_intersect (tmpl, self->probed_srccaps);
        gst_caps_unref (tmpl);
      } else
        result = gst_pad_get_pad_template_caps (pad);

      if (filter) {
        GstCaps *tmp = result;
        result =
            gst_caps_intersect_full (filter, tmp, GST_CAPS_INTERSECT_FIRST);
        gst_caps_unref (tmp);
      }

      GST_DEBUG_OBJECT (self, "Returning src caps %" GST_PTR_FORMAT, result);

      gst_query_set_caps_result (query, result);
      gst_caps_unref (result);
      break;
    }

    default:
      ret = GST_VIDEO_ENCODER_CLASS (parent_class)->src_query (encoder, query);
      break;
  }

  return ret;
}

static gboolean
gst_v4l2_video_enc_sink_query (GstVideoEncoder * encoder, GstQuery * query)
{
  gboolean ret = TRUE;
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);

  switch (GST_QUERY_TYPE (query)) {
    case GST_QUERY_CAPS:{
      GstCaps *filter, *result = NULL;
      GstPad *pad = GST_VIDEO_ENCODER_SINK_PAD (encoder);

      gst_query_parse_caps (query, &filter);

      if (self->probed_sinkcaps)
        result = gst_caps_ref (self->probed_sinkcaps);
      else
        result = gst_pad_get_pad_template_caps (pad);

      if (filter) {
        GstCaps *tmp = result;
        result =
            gst_caps_intersect_full (filter, tmp, GST_CAPS_INTERSECT_FIRST);
        gst_caps_unref (tmp);
      }

      GST_DEBUG_OBJECT (self, "Returning sink caps %" GST_PTR_FORMAT, result);

      gst_query_set_caps_result (query, result);
      gst_caps_unref (result);
      break;
    }

    default:
      ret = GST_VIDEO_ENCODER_CLASS (parent_class)->sink_query (encoder, query);
      break;
  }

  return ret;
}

static gboolean
gst_v4l2_video_enc_sink_event (GstVideoEncoder * encoder, GstEvent * event)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (encoder);
  gboolean ret;
  GstEventType type = GST_EVENT_TYPE (event);

  switch (type) {
    case GST_EVENT_FLUSH_START:
      GST_DEBUG_OBJECT (self, "flush start");
      gst_v4l2_object_unlock (self->v4l2output);
      gst_v4l2_object_unlock (self->v4l2capture);
      break;
    default:
      break;
  }

  ret = GST_VIDEO_ENCODER_CLASS (parent_class)->sink_event (encoder, event);

  switch (type) {
    case GST_EVENT_FLUSH_START:
      gst_pad_stop_task (encoder->srcpad);
      GST_DEBUG_OBJECT (self, "flush start done");
    default:
      break;
  }

  return ret;
}

static GstStateChangeReturn
gst_v4l2_video_enc_change_state (GstElement * element,
    GstStateChange transition)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (element);

  if (transition == GST_STATE_CHANGE_PAUSED_TO_READY) {
    g_atomic_int_set (&self->active, FALSE);
    gst_v4l2_object_unlock (self->v4l2output);
    gst_v4l2_object_unlock (self->v4l2capture);
  }

  return GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
}


static void
gst_v4l2_video_enc_dispose (GObject * object)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (object);

  gst_caps_replace (&self->probed_sinkcaps, NULL);
  gst_caps_replace (&self->probed_srccaps, NULL);

  G_OBJECT_CLASS (parent_class)->dispose (object);
}

static void
gst_v4l2_video_enc_finalize (GObject * object)
{
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (object);

  gst_v4l2_object_destroy (self->v4l2capture);
  gst_v4l2_object_destroy (self->v4l2output);

  G_OBJECT_CLASS (parent_class)->finalize (object);
}


static void
gst_v4l2_video_enc_init (GstV4l2VideoEnc * self)
{
  /* V4L2 object are created in subinstance_init */
}

static void
gst_v4l2_video_enc_subinstance_init (GTypeInstance * instance, gpointer g_class)
{
  GstV4l2VideoEncClass *klass = GST_V4L2_VIDEO_ENC_CLASS (g_class);
  GstV4l2VideoEnc *self = GST_V4L2_VIDEO_ENC (instance);

  self->v4l2output = gst_v4l2_object_new (GST_ELEMENT (self),
      GST_OBJECT (GST_VIDEO_ENCODER_SINK_PAD (self)),
      V4L2_BUF_TYPE_VIDEO_OUTPUT, klass->default_device,
      gst_v4l2_get_output, gst_v4l2_set_output, NULL);
  self->v4l2output->no_initial_format = TRUE;
  self->v4l2output->keep_aspect = FALSE;

  self->v4l2capture = gst_v4l2_object_new (GST_ELEMENT (self),
      GST_OBJECT (GST_VIDEO_ENCODER_SRC_PAD (self)),
      V4L2_BUF_TYPE_VIDEO_CAPTURE, klass->default_device,
      gst_v4l2_get_input, gst_v4l2_set_input, NULL);
}

static void
gst_v4l2_video_enc_class_init (GstV4l2VideoEncClass * klass)
{
  GstElementClass *element_class;
  GObjectClass *gobject_class;
  GstVideoEncoderClass *video_encoder_class;

  parent_class = g_type_class_peek_parent (klass);

  element_class = (GstElementClass *) klass;
  gobject_class = (GObjectClass *) klass;
  video_encoder_class = (GstVideoEncoderClass *) klass;

  GST_DEBUG_CATEGORY_INIT (gst_v4l2_video_enc_debug, "v4l2videoenc", 0,
      "V4L2 Video Encoder");

  gobject_class->dispose = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_dispose);
  gobject_class->finalize = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_finalize);
  gobject_class->set_property =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_set_property);
  gobject_class->get_property =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_get_property);

  video_encoder_class->open = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_open);
  video_encoder_class->close = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_close);
  video_encoder_class->start = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_start);
  video_encoder_class->stop = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_stop);
  video_encoder_class->finish = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_finish);
  video_encoder_class->flush = GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_flush);
  video_encoder_class->set_format =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_set_format);
  video_encoder_class->negotiate =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_negotiate);
  video_encoder_class->decide_allocation =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_decide_allocation);
  video_encoder_class->propose_allocation =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_propose_allocation);
  video_encoder_class->sink_query =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_sink_query);
  video_encoder_class->src_query =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_src_query);
  video_encoder_class->sink_event =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_sink_event);
  video_encoder_class->handle_frame =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_handle_frame);

  element_class->change_state =
      GST_DEBUG_FUNCPTR (gst_v4l2_video_enc_change_state);

  gst_v4l2_object_install_m2m_properties_helper (gobject_class);
}

static void
gst_v4l2_video_enc_subclass_init (gpointer g_class, gpointer data)
{
  GstV4l2VideoEncClass *klass = GST_V4L2_VIDEO_ENC_CLASS (g_class);
  GstElementClass *element_class = GST_ELEMENT_CLASS (g_class);
  GstV4l2VideoEncCData *cdata = data;

  klass->default_device = cdata->device;
  klass->codec = cdata->codec;

  gst_element_class_add_pad_template (element_class,
      gst_pad_template_new ("sink", GST_PAD_SINK, GST_PAD_ALWAYS,
          cdata->sink_caps));
  gst_element_class_add_pad_template (element_class,
      gst_pad_template_new ("src", GST_PAD_SRC, GST_PAD_ALWAYS,
          cdata->src_caps));

  gst_caps_unref (cdata->sink_caps);
  gst_caps_unref (cdata->src_caps);
  g_free (cdata);
}

/* Probing functions */
gboolean
gst_v4l2_is_video_enc (GstCaps * sink_caps, GstCaps * src_caps,
    GstCaps * codec_caps)
{
  gboolean ret = FALSE;
  gboolean (*check_caps) (const GstCaps *, const GstCaps *);

  if (codec_caps) {
    check_caps = gst_caps_can_intersect;
  } else {
    codec_caps = gst_v4l2_object_get_codec_caps ();
    check_caps = gst_caps_is_subset;
  }

  if (gst_caps_is_subset (sink_caps, gst_v4l2_object_get_raw_caps ())
      && check_caps (src_caps, codec_caps))
    ret = TRUE;

  return ret;
}

void
gst_v4l2_video_enc_register (GstPlugin * plugin, GType type,
    const char *codec_name, const gchar * basename, const gchar * device_path,
    const GstV4l2Codec * codec, gint video_fd, GstCaps * sink_caps,
    GstCaps * codec_caps, GstCaps * src_caps)
{
  GstCaps *filtered_caps;
  GTypeQuery type_query;
  GTypeInfo type_info = { 0, };
  GType subtype;
  gchar *type_name;
  GstV4l2VideoEncCData *cdata;
  GValue value = G_VALUE_INIT;

  filtered_caps = gst_caps_intersect (src_caps, codec_caps);

  if (codec != NULL && video_fd != -1) {
    if (gst_v4l2_codec_probe_levels (codec, video_fd, &value)) {
      gst_caps_set_value (filtered_caps, "level", &value);
      g_value_unset (&value);
    }

    if (gst_v4l2_codec_probe_profiles (codec, video_fd, &value)) {
      gst_caps_set_value (filtered_caps, "profile", &value);
      g_value_unset (&value);
    }
  }

  cdata = g_new0 (GstV4l2VideoEncCData, 1);
  cdata->device = g_strdup (device_path);
  cdata->sink_caps = gst_caps_ref (sink_caps);
  cdata->src_caps = gst_caps_ref (filtered_caps);
  cdata->codec = codec;

  g_type_query (type, &type_query);
  memset (&type_info, 0, sizeof (type_info));
  type_info.class_size = type_query.class_size;
  type_info.instance_size = type_query.instance_size;
  type_info.class_init = gst_v4l2_video_enc_subclass_init;
  type_info.class_data = cdata;
  type_info.instance_init = gst_v4l2_video_enc_subinstance_init;

  /* The first encoder to be registered should use a constant name, like
   * v4l2h264enc, for any additional encoders, we create unique names. Encoder
   * names may change between boots, so this should help gain stable names for
   * the most common use cases. */
  type_name = g_strdup_printf ("v4l2%senc", codec_name);

  if (g_type_from_name (type_name) != 0) {
    g_free (type_name);
    type_name = g_strdup_printf ("v4l2%s%senc", basename, codec_name);
  }

  subtype = g_type_register_static (type, type_name, &type_info, 0);

  if (!gst_element_register (plugin, type_name, GST_RANK_PRIMARY + 1, subtype))
    GST_WARNING ("Failed to register plugin '%s'", type_name);

  g_free (type_name);
}