/* GStreamer
 * Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
 *
 * 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 */
/**
 * SECTION:element-pngdec
 *
 * Decodes png images. If there is no framerate set on sink caps, it sends EOS
 * after the first picture.
 */

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

#include "gstpngdec.h"

#include <stdlib.h>
#include <string.h>
#include <gst/video/video.h>
#include <gst/video/gstvideometa.h>
#include <gst/video/gstvideopool.h>
#include <gst/gst-i18n-plugin.h>

GST_DEBUG_CATEGORY_STATIC (pngdec_debug);
#define GST_CAT_DEFAULT pngdec_debug

static gboolean gst_pngdec_libpng_init (GstPngDec * pngdec);
static gboolean gst_pngdec_libpng_clear (GstPngDec * pngdec);

static GstStateChangeReturn gst_pngdec_change_state (GstElement * element,
    GstStateChange transition);

static gboolean gst_pngdec_sink_activate_mode (GstPad * sinkpad,
    GstObject * parent, GstPadMode mode, gboolean active);
static gboolean gst_pngdec_sink_activate (GstPad * sinkpad, GstObject * parent);

static GstFlowReturn gst_pngdec_caps_create_and_set (GstPngDec * pngdec);

static void gst_pngdec_task (GstPad * pad);
static GstFlowReturn gst_pngdec_chain (GstPad * pad, GstObject * parent,
    GstBuffer * buffer);
static gboolean gst_pngdec_sink_event (GstPad * pad, GstObject * parent,
    GstEvent * event);
static gboolean gst_pngdec_sink_setcaps (GstPngDec * pngdec, GstCaps * caps);

static GstFlowReturn gst_pngdec_negotiate_pool (GstPngDec * dec,
    GstCaps * caps, GstVideoInfo * info);

static GstStaticPadTemplate gst_pngdec_src_pad_template =
GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS (GST_VIDEO_CAPS_MAKE
        ("{ RGBA, RGB, ARGB64, GRAY8, GRAY16_BE }"))
    );

static GstStaticPadTemplate gst_pngdec_sink_pad_template =
GST_STATIC_PAD_TEMPLATE ("sink",
    GST_PAD_SINK,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("image/png")
    );

#define gst_pngdec_parent_class parent_class
G_DEFINE_TYPE (GstPngDec, gst_pngdec, GST_TYPE_ELEMENT);

static void
gst_pngdec_class_init (GstPngDecClass * klass)
{
  GstElementClass *gstelement_class;

  gstelement_class = (GstElementClass *) klass;

  gstelement_class->change_state = GST_DEBUG_FUNCPTR (gst_pngdec_change_state);

  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&gst_pngdec_src_pad_template));
  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&gst_pngdec_sink_pad_template));
  gst_element_class_set_details_simple (gstelement_class, "PNG image decoder",
      "Codec/Decoder/Image",
      "Decode a png video frame to a raw image",
      "Wim Taymans <wim@fluendo.com>");

  GST_DEBUG_CATEGORY_INIT (pngdec_debug, "pngdec", 0, "PNG image decoder");
}

static void
gst_pngdec_init (GstPngDec * pngdec)
{
  pngdec->sinkpad =
      gst_pad_new_from_static_template (&gst_pngdec_sink_pad_template, "sink");
  gst_pad_set_activate_function (pngdec->sinkpad,
      GST_DEBUG_FUNCPTR (gst_pngdec_sink_activate));
  gst_pad_set_activatemode_function (pngdec->sinkpad,
      GST_DEBUG_FUNCPTR (gst_pngdec_sink_activate_mode));
  gst_pad_set_chain_function (pngdec->sinkpad,
      GST_DEBUG_FUNCPTR (gst_pngdec_chain));
  gst_pad_set_event_function (pngdec->sinkpad,
      GST_DEBUG_FUNCPTR (gst_pngdec_sink_event));
  gst_element_add_pad (GST_ELEMENT (pngdec), pngdec->sinkpad);

  pngdec->srcpad =
      gst_pad_new_from_static_template (&gst_pngdec_src_pad_template, "src");
  gst_pad_use_fixed_caps (pngdec->srcpad);
  gst_element_add_pad (GST_ELEMENT (pngdec), pngdec->srcpad);

  pngdec->buffer_out = NULL;
  pngdec->png = NULL;
  pngdec->info = NULL;
  pngdec->endinfo = NULL;
  pngdec->setup = FALSE;

  pngdec->color_type = -1;
  pngdec->width = -1;
  pngdec->height = -1;
  pngdec->fps_n = 0;
  pngdec->fps_d = 1;

  pngdec->in_timestamp = GST_CLOCK_TIME_NONE;
  pngdec->in_duration = GST_CLOCK_TIME_NONE;

  gst_segment_init (&pngdec->segment, GST_FORMAT_UNDEFINED);

  pngdec->image_ready = FALSE;
}

static void
user_error_fn (png_structp png_ptr, png_const_charp error_msg)
{
  GST_ERROR ("%s", error_msg);
}

static void
user_warning_fn (png_structp png_ptr, png_const_charp warning_msg)
{
  GST_WARNING ("%s", warning_msg);
}

static void
user_info_callback (png_structp png_ptr, png_infop info)
{
  GstPngDec *pngdec = NULL;
  GstFlowReturn ret = GST_FLOW_OK;
  GstBuffer *buffer = NULL;

  pngdec = GST_PNGDEC (png_get_io_ptr (png_ptr));

  GST_LOG ("info ready");

  /* Generate the caps and configure */
  ret = gst_pngdec_caps_create_and_set (pngdec);
  if (ret != GST_FLOW_OK) {
    goto beach;
  }

  if (gst_pad_check_reconfigure (pngdec->srcpad)) {
    GstCaps *caps;

    caps = gst_pad_get_current_caps (pngdec->srcpad);
    gst_pngdec_negotiate_pool (pngdec, caps, &pngdec->vinfo);
    gst_caps_unref (caps);
  }

  /* Allocate output buffer */
  g_assert (pngdec->pool);
  ret = gst_buffer_pool_acquire_buffer (pngdec->pool, &buffer, NULL);
  if (ret != GST_FLOW_OK) {
    GST_DEBUG_OBJECT (pngdec, "failed to acquire buffer");
    ret = GST_FLOW_ERROR;
    goto beach;
  }

  pngdec->buffer_out = buffer;

beach:
  pngdec->ret = ret;
}

static void
user_endrow_callback (png_structp png_ptr, png_bytep new_row,
    png_uint_32 row_num, int pass)
{
  GstPngDec *pngdec = NULL;

  pngdec = GST_PNGDEC (png_get_io_ptr (png_ptr));

  /* FIXME: implement interlaced pictures */

  /* If buffer_out doesn't exist, it means buffer_alloc failed, which 
   * will already have set the return code */
  if (GST_IS_BUFFER (pngdec->buffer_out)) {
    GstVideoFrame frame;
    GstBuffer *buffer = pngdec->buffer_out;
    size_t offset;
    gint width;
    guint8 *data;

    if (!gst_video_frame_map (&frame, &pngdec->vinfo, buffer, GST_MAP_WRITE)) {
      pngdec->ret = GST_FLOW_ERROR;
      return;
    }

    data = GST_VIDEO_FRAME_COMP_DATA (&frame, 0);
    offset = row_num * GST_VIDEO_FRAME_COMP_STRIDE (&frame, 0);
    GST_LOG ("got row %u, copying in buffer %p at offset %" G_GSIZE_FORMAT,
        (guint) row_num, pngdec->buffer_out, offset);
    width = GST_ROUND_UP_4 (png_get_rowbytes (pngdec->png, pngdec->info));
    memcpy (data + offset, new_row, width);
    gst_video_frame_unmap (&frame);
    pngdec->ret = GST_FLOW_OK;
  }
}

static gboolean
buffer_clip (GstPngDec * dec, GstBuffer * buffer)
{
  gboolean res = TRUE;
  guint64 cstart, cstop;

  if ((!GST_CLOCK_TIME_IS_VALID (GST_BUFFER_TIMESTAMP (buffer))) ||
      (!GST_CLOCK_TIME_IS_VALID (GST_BUFFER_DURATION (buffer))) ||
      (dec->segment.format != GST_FORMAT_TIME))
    goto beach;

  cstart = GST_BUFFER_TIMESTAMP (buffer);
  cstop = GST_BUFFER_DURATION (buffer);

  if ((res = gst_segment_clip (&dec->segment, GST_FORMAT_TIME,
              cstart, cstart + cstop, &cstart, &cstop))) {
    GST_BUFFER_TIMESTAMP (buffer) = cstart;
    GST_BUFFER_DURATION (buffer) = cstop - cstart;
  }

beach:
  return res;
}

static void
user_end_callback (png_structp png_ptr, png_infop info)
{
  GstPngDec *pngdec = NULL;

  pngdec = GST_PNGDEC (png_get_io_ptr (png_ptr));

  GST_LOG_OBJECT (pngdec, "and we are done reading this image");

  if (!pngdec->buffer_out)
    return;

  if (GST_CLOCK_TIME_IS_VALID (pngdec->in_timestamp))
    GST_BUFFER_TIMESTAMP (pngdec->buffer_out) = pngdec->in_timestamp;
  if (GST_CLOCK_TIME_IS_VALID (pngdec->in_duration))
    GST_BUFFER_DURATION (pngdec->buffer_out) = pngdec->in_duration;

  /* buffer clipping */
  if (buffer_clip (pngdec, pngdec->buffer_out)) {
    /* Push our buffer and then EOS if needed */
    GST_LOG_OBJECT (pngdec, "pushing buffer with ts=%" GST_TIME_FORMAT,
        GST_TIME_ARGS (GST_BUFFER_TIMESTAMP (pngdec->buffer_out)));

    pngdec->ret = gst_pad_push (pngdec->srcpad, pngdec->buffer_out);
  } else {
    GST_LOG_OBJECT (pngdec, "dropped decoded buffer");
    gst_buffer_unref (pngdec->buffer_out);
  }
  pngdec->buffer_out = NULL;
  pngdec->image_ready = TRUE;
}

static void
user_read_data (png_structp png_ptr, png_bytep data, png_size_t length)
{
  GstPngDec *pngdec;
  GstBuffer *buffer = NULL;
  GstFlowReturn ret = GST_FLOW_OK;
  guint size;

  pngdec = GST_PNGDEC (png_get_io_ptr (png_ptr));

  GST_LOG ("reading %" G_GSIZE_FORMAT " bytes of data at offset %d", length,
      pngdec->offset);

  ret = gst_pad_pull_range (pngdec->sinkpad, pngdec->offset, length, &buffer);
  if (ret != GST_FLOW_OK)
    goto pause;

  size = gst_buffer_get_size (buffer);

  if (size != length)
    goto short_buffer;

  gst_buffer_extract (buffer, 0, data, size);
  gst_buffer_unref (buffer);

  pngdec->offset += length;

  return;

  /* ERRORS */
pause:
  {
    GST_INFO_OBJECT (pngdec, "pausing task, reason %s",
        gst_flow_get_name (ret));
    gst_pad_pause_task (pngdec->sinkpad);
    if (ret == GST_FLOW_EOS) {
      gst_pad_push_event (pngdec->srcpad, gst_event_new_eos ());
    } else if (ret < GST_FLOW_EOS || ret == GST_FLOW_NOT_LINKED) {
      GST_ELEMENT_ERROR (pngdec, STREAM, FAILED,
          (_("Internal data stream error.")),
          ("stream stopped, reason %s", gst_flow_get_name (ret)));
      gst_pad_push_event (pngdec->srcpad, gst_event_new_eos ());
    }
    png_error (png_ptr, "Internal data stream error.");
    return;
  }
short_buffer:
  {
    gst_buffer_unref (buffer);
    GST_ELEMENT_ERROR (pngdec, STREAM, FAILED,
        (_("Internal data stream error.")),
        ("Read %u, needed %" G_GSIZE_FORMAT "bytes", size, length));
    ret = GST_FLOW_ERROR;
    goto pause;
  }
}

static GstFlowReturn
gst_pngdec_negotiate_pool (GstPngDec * dec, GstCaps * caps, GstVideoInfo * info)
{
  GstQuery *query;
  GstBufferPool *pool;
  guint size, min, max;
  GstStructure *config;

  /* find a pool for the negotiated caps now */
  query = gst_query_new_allocation (caps, TRUE);

  if (!gst_pad_peer_query (dec->srcpad, query)) {
    GST_DEBUG_OBJECT (dec, "didn't get downstream ALLOCATION hints");
  }

  if (gst_query_get_n_allocation_pools (query) > 0) {
    /* we got configuration from our peer, parse them */
    gst_query_parse_nth_allocation_pool (query, 0, &pool, &size, &min, &max);
    size = MAX (size, info->size);
  } else {
    pool = NULL;
    size = info->size;
    min = max = 0;
  }

  if (pool == NULL) {
    /* we did not get a pool, make one ourselves then */
    pool = gst_video_buffer_pool_new ();
  }

  if (dec->pool) {
    gst_buffer_pool_set_active (dec->pool, TRUE);
    gst_object_unref (dec->pool);
  }
  dec->pool = pool;

  config = gst_buffer_pool_get_config (pool);
  gst_buffer_pool_config_set_params (config, caps, size, min, max);

  if (gst_query_has_allocation_meta (query, GST_VIDEO_META_API_TYPE)) {
    /* just set the option, if the pool can support it we will transparently use
     * it through the video info API. We could also see if the pool support this
     * option and only activate it then. */
    gst_buffer_pool_config_add_option (config,
        GST_BUFFER_POOL_OPTION_VIDEO_META);
  }
  gst_buffer_pool_set_config (pool, config);

  /* and activate */
  gst_buffer_pool_set_active (pool, TRUE);

  gst_query_unref (query);

  return GST_FLOW_OK;
}

static GstFlowReturn
gst_pngdec_caps_create_and_set (GstPngDec * pngdec)
{
  GstFlowReturn ret = GST_FLOW_OK;
  GstCaps *caps = NULL, *res = NULL;
  GstPadTemplate *templ = NULL;
  gint bpc = 0, color_type;
  png_uint_32 width, height;
  GstVideoFormat format;
  GstVideoInfo vinfo = { 0, };

  g_return_val_if_fail (GST_IS_PNGDEC (pngdec), GST_FLOW_ERROR);

  /* Get bits per channel */
  bpc = png_get_bit_depth (pngdec->png, pngdec->info);

  /* Get Color type */
  color_type = png_get_color_type (pngdec->png, pngdec->info);

  /* Add alpha channel if 16-bit depth, but not for GRAY images */
  if ((bpc > 8) && (color_type != PNG_COLOR_TYPE_GRAY)) {
    png_set_add_alpha (pngdec->png, 0xffff, PNG_FILLER_BEFORE);
    png_set_swap (pngdec->png);
  }
#if 0
  /* We used to have this HACK to reverse the outgoing bytes, but the problem
   * that originally required the hack seems to have been in ffmpegcolorspace's
   * RGBA descriptions. It doesn't seem needed now that's fixed, but might
   * still be needed on big-endian systems, I'm not sure. J.S. 6/7/2007 */
  if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
    png_set_bgr (pngdec->png);
#endif

  /* Gray scale with alpha channel converted to RGB */
  if (color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
    GST_LOG_OBJECT (pngdec,
        "converting grayscale png with alpha channel to RGB");
    png_set_gray_to_rgb (pngdec->png);
  }

  /* Gray scale converted to upscaled to 8 bits */
  if ((color_type == PNG_COLOR_TYPE_GRAY_ALPHA) ||
      (color_type == PNG_COLOR_TYPE_GRAY)) {
    if (bpc < 8) {              /* Convert to 8 bits */
      GST_LOG_OBJECT (pngdec, "converting grayscale image to 8 bits");
#if PNG_LIBPNG_VER < 10400
      png_set_gray_1_2_4_to_8 (pngdec->png);
#else
      png_set_expand_gray_1_2_4_to_8 (pngdec->png);
#endif
    }
  }

  /* Palette converted to RGB */
  if (color_type == PNG_COLOR_TYPE_PALETTE) {
    GST_LOG_OBJECT (pngdec, "converting palette png to RGB");
    png_set_palette_to_rgb (pngdec->png);
  }

  /* Update the info structure */
  png_read_update_info (pngdec->png, pngdec->info);

  /* Get IHDR header again after transformation settings */

  png_get_IHDR (pngdec->png, pngdec->info, &width, &height,
      &bpc, &pngdec->color_type, NULL, NULL, NULL);

  pngdec->width = width;
  pngdec->height = height;

  GST_LOG_OBJECT (pngdec, "this is a %dx%d PNG image", pngdec->width,
      pngdec->height);

  switch (pngdec->color_type) {
    case PNG_COLOR_TYPE_RGB:
      GST_LOG_OBJECT (pngdec, "we have no alpha channel, depth is 24 bits");
      format = GST_VIDEO_FORMAT_RGB;
      break;
    case PNG_COLOR_TYPE_RGB_ALPHA:
      GST_LOG_OBJECT (pngdec, "we have an alpha channel, depth is 32 bits");
      if (bpc == 1)
        format = GST_VIDEO_FORMAT_RGBA;
      else
        format = GST_VIDEO_FORMAT_ARGB64;
      break;
    case PNG_COLOR_TYPE_GRAY:
      GST_LOG_OBJECT (pngdec,
          "We have an gray image, depth is 8 or 16 (be) bits");
      if (bpc == 1)
        format = GST_VIDEO_FORMAT_GRAY8;
      else
        format = GST_VIDEO_FORMAT_GRAY16_BE;
      break;
    default:
      GST_ELEMENT_ERROR (pngdec, STREAM, NOT_IMPLEMENTED, (NULL),
          ("pngdec does not support this color type"));
      ret = GST_FLOW_NOT_SUPPORTED;
      goto beach;
  }

  gst_video_info_set_format (&vinfo, format, pngdec->width, pngdec->height);
  vinfo.fps_n = pngdec->fps_n;
  vinfo.fps_d = pngdec->fps_d;
  vinfo.par_n = 1;
  vinfo.par_d = 1;

  if (memcmp (&vinfo, &pngdec->vinfo, sizeof (vinfo)) == 0) {
    GST_DEBUG_OBJECT (pngdec, "video info unchanged, skip negotiation");
    ret = GST_FLOW_OK;
    goto beach;
  }

  pngdec->vinfo = vinfo;

  caps = gst_video_info_to_caps (&pngdec->vinfo);

  templ = gst_static_pad_template_get (&gst_pngdec_src_pad_template);

  res = gst_caps_intersect (caps, gst_pad_template_get_caps (templ));

  gst_caps_unref (caps);
  gst_object_unref (templ);

  if (!gst_pad_set_caps (pngdec->srcpad, res))
    ret = GST_FLOW_NOT_NEGOTIATED;

  /* clear pending reconfigure */
  gst_pad_check_reconfigure (pngdec->srcpad);

  GST_DEBUG_OBJECT (pngdec, "our caps %" GST_PTR_FORMAT, res);
  gst_pngdec_negotiate_pool (pngdec, res, &pngdec->vinfo);

  gst_caps_unref (res);

  /* Push a newsegment event */
  if (pngdec->need_newsegment) {
    gst_segment_init (&pngdec->segment, GST_FORMAT_TIME);
    gst_pad_push_event (pngdec->srcpad,
        gst_event_new_segment (&pngdec->segment));
    pngdec->need_newsegment = FALSE;
  }

beach:
  return ret;
}

static void
gst_pngdec_task (GstPad * pad)
{
  GstPngDec *pngdec;
  GstBuffer *buffer = NULL;
  gint i = 0;
  png_bytep *rows, inp = NULL;
  GstFlowReturn ret = GST_FLOW_OK;
  GstVideoFrame frame;

  pngdec = GST_PNGDEC (GST_OBJECT_PARENT (pad));

  GST_LOG_OBJECT (pngdec, "read frame");

  /* Let libpng come back here on error */
  if (setjmp (png_jmpbuf (pngdec->png))) {
    ret = GST_FLOW_ERROR;
    goto pause;
  }

  /* Set reading callback */
  png_set_read_fn (pngdec->png, pngdec, user_read_data);

  /* Read info */
  png_read_info (pngdec->png, pngdec->info);

  pngdec->fps_n = 0;
  pngdec->fps_d = 1;

  /* Generate the caps and configure */
  ret = gst_pngdec_caps_create_and_set (pngdec);
  if (ret != GST_FLOW_OK) {
    goto pause;
  }

  /* Allocate output buffer */
  g_assert (pngdec->pool);
  ret = gst_buffer_pool_acquire_buffer (pngdec->pool, &buffer, NULL);
  if (ret != GST_FLOW_OK)
    goto pause;

  rows = (png_bytep *) g_malloc (sizeof (png_bytep) * pngdec->height);

  if (!gst_video_frame_map (&frame, &pngdec->vinfo, buffer, GST_MAP_WRITE))
    goto invalid_frame;

  inp = GST_VIDEO_FRAME_COMP_DATA (&frame, 0);

  for (i = 0; i < pngdec->height; i++) {
    rows[i] = inp;
    inp += GST_VIDEO_FRAME_COMP_STRIDE (&frame, 0);
  }

  /* Read the actual picture */
  png_read_image (pngdec->png, rows);
  g_free (rows);

  gst_video_frame_unmap (&frame);
  inp = NULL;

  /* Push the raw RGB frame */
  ret = gst_pad_push (pngdec->srcpad, buffer);
  buffer = NULL;
  if (ret != GST_FLOW_OK)
    goto pause;

  /* And we are done */
  gst_pad_pause_task (pngdec->sinkpad);
  gst_pad_push_event (pngdec->srcpad, gst_event_new_eos ());
  return;

pause:
  {
    if (inp)
      gst_video_frame_unmap (&frame);
    if (buffer)
      gst_buffer_unref (buffer);
    GST_INFO_OBJECT (pngdec, "pausing task, reason %s",
        gst_flow_get_name (ret));
    gst_pad_pause_task (pngdec->sinkpad);
    if (ret == GST_FLOW_EOS) {
      gst_pad_push_event (pngdec->srcpad, gst_event_new_eos ());
    } else if (ret == GST_FLOW_NOT_LINKED || ret < GST_FLOW_EOS) {
      GST_ELEMENT_ERROR (pngdec, STREAM, FAILED,
          (_("Internal data stream error.")),
          ("stream stopped, reason %s", gst_flow_get_name (ret)));
      gst_pad_push_event (pngdec->srcpad, gst_event_new_eos ());
    }
  }
invalid_frame:
  {
    GST_DEBUG_OBJECT (pngdec, "could not map video frame");
    ret = GST_FLOW_ERROR;
    goto pause;
  }
}

static GstFlowReturn
gst_pngdec_chain (GstPad * pad, GstObject * parent, GstBuffer * buffer)
{
  GstPngDec *pngdec;
  GstFlowReturn ret = GST_FLOW_OK;
  GstMapInfo map = GST_MAP_INFO_INIT;

  pngdec = GST_PNGDEC (parent);

  if (G_UNLIKELY (!pngdec->setup))
    goto not_configured;

  /* Something is going wrong in our callbacks */
  ret = pngdec->ret;
  if (G_UNLIKELY (ret != GST_FLOW_OK)) {
    GST_WARNING_OBJECT (pngdec, "we have a pending return code of %d", ret);
    goto beach;
  }

  /* Let libpng come back here on error */
  if (setjmp (png_jmpbuf (pngdec->png))) {
    GST_WARNING_OBJECT (pngdec, "error during decoding");
    ret = GST_FLOW_ERROR;
    goto beach;
  }

  pngdec->in_timestamp = GST_BUFFER_TIMESTAMP (buffer);
  pngdec->in_duration = GST_BUFFER_DURATION (buffer);

  gst_buffer_map (buffer, &map, GST_MAP_READ);

  GST_LOG_OBJECT (pngdec, "Got buffer, size=%d", (gint) map.size);

  /* Progressive loading of the PNG image */
  png_process_data (pngdec->png, pngdec->info, map.data, map.size);

  if (pngdec->image_ready) {
    if (pngdec->framed) {
      /* Reset ourselves for the next frame */
      gst_pngdec_libpng_clear (pngdec);
      gst_pngdec_libpng_init (pngdec);
      GST_LOG_OBJECT (pngdec, "setting up callbacks for next frame");
      png_set_progressive_read_fn (pngdec->png, pngdec,
          user_info_callback, user_endrow_callback, user_end_callback);
    } else {
      GST_LOG_OBJECT (pngdec, "sending EOS");
      pngdec->ret = gst_pad_push_event (pngdec->srcpad, gst_event_new_eos ());
    }
    pngdec->image_ready = FALSE;
  }

  /* grab new return code */
  ret = pngdec->ret;

beach:
  if (G_LIKELY (map.data))
    gst_buffer_unmap (buffer, &map);

  /* And release the buffer */
  gst_buffer_unref (buffer);

  return ret;

  /* ERRORS */
not_configured:
  {
    GST_LOG_OBJECT (pngdec, "we are not configured yet");
    ret = GST_FLOW_FLUSHING;
    goto beach;
  }
}

static gboolean
gst_pngdec_sink_setcaps (GstPngDec * pngdec, GstCaps * caps)
{
  GstStructure *s;
  gint num, denom;

  s = gst_caps_get_structure (caps, 0);
  if (gst_structure_get_fraction (s, "framerate", &num, &denom)) {
    GST_DEBUG_OBJECT (pngdec, "framed input");
    pngdec->framed = TRUE;
    pngdec->fps_n = num;
    pngdec->fps_d = denom;
  } else {
    GST_DEBUG_OBJECT (pngdec, "single picture input");
    pngdec->framed = FALSE;
    pngdec->fps_n = 0;
    pngdec->fps_d = 1;
  }

  return TRUE;
}

static gboolean
gst_pngdec_sink_event (GstPad * pad, GstObject * parent, GstEvent * event)
{
  GstPngDec *pngdec;
  gboolean res;

  pngdec = GST_PNGDEC (parent);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_SEGMENT:{
      gst_event_copy_segment (event, &pngdec->segment);

      GST_LOG_OBJECT (pngdec, "SEGMENT %" GST_SEGMENT_FORMAT, &pngdec->segment);

      if (pngdec->segment.format == GST_FORMAT_TIME) {
        pngdec->need_newsegment = FALSE;
        res = gst_pad_push_event (pngdec->srcpad, event);
      } else {
        gst_event_unref (event);
        res = TRUE;
      }
      break;
    }
    case GST_EVENT_FLUSH_STOP:
    {
      gst_pngdec_libpng_clear (pngdec);
      gst_pngdec_libpng_init (pngdec);
      png_set_progressive_read_fn (pngdec->png, pngdec,
          user_info_callback, user_endrow_callback, user_end_callback);
      pngdec->ret = GST_FLOW_OK;
      gst_segment_init (&pngdec->segment, GST_FORMAT_UNDEFINED);
      res = gst_pad_push_event (pngdec->srcpad, event);
      break;
    }
    case GST_EVENT_EOS:
    {
      GST_LOG_OBJECT (pngdec, "EOS");
      gst_pngdec_libpng_clear (pngdec);
      pngdec->ret = GST_FLOW_EOS;
      res = gst_pad_push_event (pngdec->srcpad, event);
      break;
    }
    case GST_EVENT_CAPS:
    {
      GstCaps *caps;

      gst_event_parse_caps (event, &caps);
      res = gst_pngdec_sink_setcaps (pngdec, caps);
      gst_event_unref (event);
      break;
    }
    default:
      res = gst_pad_push_event (pngdec->srcpad, event);
      break;
  }

  return res;
}


/* Clean up the libpng structures */
static gboolean
gst_pngdec_libpng_clear (GstPngDec * pngdec)
{
  png_infopp info = NULL, endinfo = NULL;

  g_return_val_if_fail (GST_IS_PNGDEC (pngdec), FALSE);

  GST_LOG ("cleaning up libpng structures");

  if (pngdec->info) {
    info = &pngdec->info;
  }

  if (pngdec->endinfo) {
    endinfo = &pngdec->endinfo;
  }

  if (pngdec->png) {
    png_destroy_read_struct (&(pngdec->png), info, endinfo);
    pngdec->png = NULL;
    pngdec->info = NULL;
    pngdec->endinfo = NULL;
  }

  pngdec->color_type = pngdec->height = pngdec->width = -1;
  pngdec->offset = 0;
  pngdec->buffer_out = NULL;

  pngdec->setup = FALSE;

  pngdec->in_timestamp = GST_CLOCK_TIME_NONE;
  pngdec->in_duration = GST_CLOCK_TIME_NONE;

  return TRUE;
}

static gboolean
gst_pngdec_libpng_init (GstPngDec * pngdec)
{
  g_return_val_if_fail (GST_IS_PNGDEC (pngdec), FALSE);

  if (pngdec->setup)
    return TRUE;

  GST_LOG ("init libpng structures");

  /* initialize png struct stuff */
  pngdec->png = png_create_read_struct (PNG_LIBPNG_VER_STRING,
      (png_voidp) NULL, user_error_fn, user_warning_fn);

  if (pngdec->png == NULL)
    goto init_failed;

  pngdec->info = png_create_info_struct (pngdec->png);
  if (pngdec->info == NULL)
    goto info_failed;

  pngdec->endinfo = png_create_info_struct (pngdec->png);
  if (pngdec->endinfo == NULL)
    goto endinfo_failed;

  pngdec->setup = TRUE;

  return TRUE;

  /* ERRORS */
init_failed:
  {
    GST_ELEMENT_ERROR (pngdec, LIBRARY, INIT, (NULL),
        ("Failed to initialize png structure"));
    return FALSE;
  }
info_failed:
  {
    gst_pngdec_libpng_clear (pngdec);
    GST_ELEMENT_ERROR (pngdec, LIBRARY, INIT, (NULL),
        ("Failed to initialize info structure"));
    return FALSE;
  }
endinfo_failed:
  {
    gst_pngdec_libpng_clear (pngdec);
    GST_ELEMENT_ERROR (pngdec, LIBRARY, INIT, (NULL),
        ("Failed to initialize endinfo structure"));
    return FALSE;
  }
}

static GstStateChangeReturn
gst_pngdec_change_state (GstElement * element, GstStateChange transition)
{
  GstStateChangeReturn ret;
  GstPngDec *pngdec;

  pngdec = GST_PNGDEC (element);

  switch (transition) {
    case GST_STATE_CHANGE_READY_TO_PAUSED:
      gst_pngdec_libpng_init (pngdec);
      pngdec->need_newsegment = TRUE;
      pngdec->framed = FALSE;
      pngdec->ret = GST_FLOW_OK;
      gst_segment_init (&pngdec->segment, GST_FORMAT_UNDEFINED);
      break;
    default:
      break;
  }

  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
  if (ret != GST_STATE_CHANGE_SUCCESS)
    return ret;

  switch (transition) {
    case GST_STATE_CHANGE_PAUSED_TO_READY:
      gst_pngdec_libpng_clear (pngdec);
      if (pngdec->pool)
        gst_object_unref (pngdec->pool);
      break;
    default:
      break;
  }

  return ret;
}

/* this function gets called when we activate ourselves in pull mode.
 * We can perform  random access to the resource and we start a task
 * to start reading */
static gboolean
gst_pngdec_sink_activate_mode (GstPad * sinkpad, GstObject * parent,
    GstPadMode mode, gboolean active)
{
  GstPngDec *pngdec = GST_PNGDEC (parent);
  gboolean res;

  switch (mode) {
    case GST_PAD_MODE_PULL:
      if (active) {
        res = gst_pad_start_task (sinkpad, (GstTaskFunction) gst_pngdec_task,
            sinkpad);
      } else {
        res = gst_pad_stop_task (sinkpad);
      }
      break;
    case GST_PAD_MODE_PUSH:
      GST_DEBUG_OBJECT (pngdec, "activating push/chain function");
      if (active) {
        pngdec->ret = GST_FLOW_OK;

        /* Let libpng come back here on error */
        if (setjmp (png_jmpbuf (pngdec->png)))
          goto setup_failed;

        GST_LOG_OBJECT (pngdec, "setting up progressive loading callbacks");
        png_set_progressive_read_fn (pngdec->png, pngdec,
            user_info_callback, user_endrow_callback, user_end_callback);
      } else {
        GST_DEBUG_OBJECT (pngdec, "deactivating push/chain function");
      }
      res = TRUE;
      break;
    default:
      res = FALSE;
      break;
  }
  return res;

setup_failed:
  {
    GST_LOG_OBJECT (pngdec, "failed setting up libpng jmpbuf");
    gst_pngdec_libpng_clear (pngdec);
    return FALSE;
  }
}

/* this function is called when the pad is activated and should start
 * processing data.
 *
 * We check if we can do random access to decide if we work push or
 * pull based.
 */
static gboolean
gst_pngdec_sink_activate (GstPad * sinkpad, GstObject * parent)
{
  GstQuery *query;
  gboolean pull_mode;

  query = gst_query_new_scheduling ();

  if (!gst_pad_peer_query (sinkpad, query)) {
    gst_query_unref (query);
    goto activate_push;
  }

  pull_mode = gst_query_has_scheduling_mode (query, GST_PAD_MODE_PULL);
  gst_query_unref (query);

  if (!pull_mode)
    goto activate_push;

  GST_DEBUG_OBJECT (sinkpad, "activating pull");
  return gst_pad_activate_mode (sinkpad, GST_PAD_MODE_PULL, TRUE);

activate_push:
  {
    GST_DEBUG_OBJECT (sinkpad, "activating push");
    return gst_pad_activate_mode (sinkpad, GST_PAD_MODE_PUSH, TRUE);
  }
}