gstreamer/sys/applemedia/avfvideosrc.m

/*
 * Copyright (C) 2010 Ole André Vadla Ravnås <oleavr@soundrop.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 "avfvideosrc.h"

#import <AVFoundation/AVFoundation.h>
#include <gst/video/video.h>
#include "coremediabuffer.h"

#define DEFAULT_DEVICE_INDEX  -1
#define DEFAULT_DO_STATS      FALSE

#define DEVICE_FPS_N          25
#define DEVICE_FPS_D          1

#define BUFFER_QUEUE_SIZE     2

GST_DEBUG_CATEGORY (gst_avf_video_src_debug);
#define GST_CAT_DEFAULT gst_avf_video_src_debug

static GstStaticPadTemplate src_template = GST_STATIC_PAD_TEMPLATE ("src",
    GST_PAD_SRC,
    GST_PAD_ALWAYS,
    GST_STATIC_CAPS ("video/x-raw, "
        "format = (string) { NV12, UYVY, YUY2 }, "
        "framerate = " GST_VIDEO_FPS_RANGE ", "
        "width = " GST_VIDEO_SIZE_RANGE ", "
        "height = " GST_VIDEO_SIZE_RANGE "; "

        "video/x-raw, "
        "format = (string) BGRA, "
        "framerate = " GST_VIDEO_FPS_RANGE ", "
        "width = " GST_VIDEO_SIZE_RANGE ", "
        "height = " GST_VIDEO_SIZE_RANGE "; "
));

typedef enum _QueueState {
  NO_BUFFERS = 1,
  HAS_BUFFER_OR_STOP_REQUEST,
} QueueState;

#define gst_avf_video_src_parent_class parent_class
G_DEFINE_TYPE (GstAVFVideoSrc, gst_avf_video_src, GST_TYPE_PUSH_SRC);

@interface GstAVFVideoSrcImpl : NSObject <AVCaptureVideoDataOutputSampleBufferDelegate> {
  GstElement *element;
  GstBaseSrc *baseSrc;
  GstPushSrc *pushSrc;

  gint deviceIndex;
  BOOL doStats;
#if !HAVE_IOS
  CGDirectDisplayID displayId;
#endif

  AVCaptureSession *session;
  AVCaptureInput *input;
  AVCaptureVideoDataOutput *output;
  AVCaptureDevice *device;

  dispatch_queue_t mainQueue;
  dispatch_queue_t workerQueue;
  NSConditionLock *bufQueueLock;
  NSMutableArray *bufQueue;
  BOOL stopRequest;

  GstCaps *caps;
  GstVideoFormat format;
  gint width, height;
  GstClockTime latency;
  guint64 offset;
  GstClockTime startAVFTimestamp;
  GstClockTime startTimestamp;

  GstClockTime lastSampling;
  guint count;
  gint fps;
  BOOL captureScreen;
  BOOL captureScreenCursor;
  BOOL captureScreenMouseClicks;

  BOOL useVideoMeta;
}

- (id)init;
- (id)initWithSrc:(GstPushSrc *)src;
- (void)finalize;

@property int deviceIndex;
@property BOOL doStats;
@property int fps;
@property BOOL captureScreen;
@property BOOL captureScreenCursor;
@property BOOL captureScreenMouseClicks;

- (BOOL)openScreenInput;
- (BOOL)openDeviceInput;
- (BOOL)openDevice;
- (void)closeDevice;
- (GstVideoFormat)getGstVideoFormat:(NSNumber *)pixel_format;
- (BOOL)getDeviceCaps:(GstCaps *)result;
- (BOOL)setDeviceCaps:(GstVideoInfo *)info;
- (BOOL)getSessionPresetCaps:(GstCaps *)result;
- (BOOL)setSessionPresetCaps:(GstVideoInfo *)info;
- (GstCaps *)getCaps;
- (BOOL)setCaps:(GstCaps *)new_caps;
- (BOOL)start;
- (BOOL)stop;
- (BOOL)unlock;
- (BOOL)unlockStop;
- (BOOL)query:(GstQuery *)query;
- (GstStateChangeReturn)changeState:(GstStateChange)transition;
- (GstFlowReturn)create:(GstBuffer **)buf;
- (void)timestampBuffer:(GstBuffer *)buf sampleBuffer:(CMSampleBufferRef)sampleBuffer;
- (void)updateStatistics;
- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection;

@end

@implementation GstAVFVideoSrcImpl

@synthesize deviceIndex, doStats, fps, captureScreen,
            captureScreenCursor, captureScreenMouseClicks;

- (id)init
{
  return [self initWithSrc:NULL];
}

- (id)initWithSrc:(GstPushSrc *)src
{
  if ((self = [super init])) {
    element = GST_ELEMENT_CAST (src);
    baseSrc = GST_BASE_SRC_CAST (src);
    pushSrc = src;

    deviceIndex = DEFAULT_DEVICE_INDEX;
    captureScreen = NO;
    captureScreenCursor = NO;
    captureScreenMouseClicks = NO;
    useVideoMeta = NO;
#if !HAVE_IOS
    displayId = kCGDirectMainDisplay;
#endif

    mainQueue =
        dispatch_queue_create ("org.freedesktop.gstreamer.avfvideosrc.main", NULL);
    workerQueue =
        dispatch_queue_create ("org.freedesktop.gstreamer.avfvideosrc.output", NULL);

    gst_base_src_set_live (baseSrc, TRUE);
    gst_base_src_set_format (baseSrc, GST_FORMAT_TIME);
  }

  return self;
}

- (void)finalize
{
  dispatch_release (mainQueue);
  mainQueue = NULL;
  dispatch_release (workerQueue);
  workerQueue = NULL;

  [super finalize];
}

- (BOOL)openDeviceInput
{
  NSString *mediaType = AVMediaTypeVideo;
  NSError *err;

  if (deviceIndex == -1) {
    device = [AVCaptureDevice defaultDeviceWithMediaType:mediaType];
    if (device == nil) {
      GST_ELEMENT_ERROR (element, RESOURCE, NOT_FOUND,
                          ("No video capture devices found"), (NULL));
      return NO;
    }
  } else {
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:mediaType];
    if (deviceIndex >= [devices count]) {
      GST_ELEMENT_ERROR (element, RESOURCE, NOT_FOUND,
                          ("Invalid video capture device index"), (NULL));
      return NO;
    }
    device = [devices objectAtIndex:deviceIndex];
  }
  g_assert (device != nil);
  [device retain];

  GST_INFO ("Opening '%s'", [[device localizedName] UTF8String]);

  input = [AVCaptureDeviceInput deviceInputWithDevice:device
                                                error:&err];
  if (input == nil) {
    GST_ELEMENT_ERROR (element, RESOURCE, BUSY,
        ("Failed to open device: %s",
        [[err localizedDescription] UTF8String]),
        (NULL));
    [device release];
    device = nil;
    return NO;
  }
  [input retain];
  return YES;
}

- (BOOL)openScreenInput
{
#if HAVE_IOS
  return NO;
#else
  GST_DEBUG_OBJECT (element, "Opening screen input");

  AVCaptureScreenInput *screenInput =
      [[AVCaptureScreenInput alloc] initWithDisplayID:displayId];


  @try {
    [screenInput setValue:[NSNumber numberWithBool:captureScreenCursor]
                 forKey:@"capturesCursor"];

  } @catch (NSException *exception) {
    if (![[exception name] isEqualToString:NSUndefinedKeyException]) {
      GST_WARNING ("An unexpected error occured: %s",
                   [[exception reason] UTF8String]);
    }
    GST_WARNING ("Capturing cursor is only supported in OS X >= 10.8");
  }
  screenInput.capturesMouseClicks = captureScreenMouseClicks;
  input = screenInput;
  [input retain];
  return YES;
#endif
}

- (BOOL)openDevice
{
  BOOL success = NO, *successPtr = &success;

  GST_DEBUG_OBJECT (element, "Opening device");

  dispatch_sync (mainQueue, ^{
    BOOL ret;

    if (captureScreen)
      ret = [self openScreenInput];
    else
      ret = [self openDeviceInput];

    if (!ret)
      return;

    output = [[AVCaptureVideoDataOutput alloc] init];
    [output setSampleBufferDelegate:self
                              queue:workerQueue];
    output.alwaysDiscardsLateVideoFrames = YES;
    output.videoSettings = nil; /* device native format */

    session = [[AVCaptureSession alloc] init];
    [session addInput:input];
    [session addOutput:output];

    *successPtr = YES;
  });

  GST_DEBUG_OBJECT (element, "Opening device %s", success ? "succeed" : "failed");

  return success;
}

- (void)closeDevice
{
  GST_DEBUG_OBJECT (element, "Closing device");

  dispatch_sync (mainQueue, ^{
    g_assert (![session isRunning]);

    [session removeInput:input];
    [session removeOutput:output];

    [session release];
    session = nil;

    [input release];
    input = nil;

    [output release];
    output = nil;

    if (!captureScreen) {
      [device release];
      device = nil;
    }

    if (caps)
      gst_caps_unref (caps);
  });
}

#define GST_AVF_CAPS_NEW(format, w, h, fps_n, fps_d)                  \
    (gst_caps_new_simple ("video/x-raw",                              \
        "width", G_TYPE_INT, w,                                       \
        "height", G_TYPE_INT, h,                                      \
        "format", G_TYPE_STRING, gst_video_format_to_string (format), \
        "framerate", GST_TYPE_FRACTION, (fps_n), (fps_d),             \
        NULL))

- (GstVideoFormat)getGstVideoFormat:(NSNumber *)pixel_format
{
  GstVideoFormat gst_format = GST_VIDEO_FORMAT_UNKNOWN;

  switch ([pixel_format integerValue]) {
  case kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange: /* 420v */
    gst_format = GST_VIDEO_FORMAT_NV12;
    break;
  case kCVPixelFormatType_422YpCbCr8: /* 2vuy */
    gst_format = GST_VIDEO_FORMAT_UYVY;
    break;
  case kCVPixelFormatType_32BGRA: /* BGRA */
    gst_format = GST_VIDEO_FORMAT_BGRA;
    break;
  case kCVPixelFormatType_422YpCbCr8_yuvs: /* yuvs */
    gst_format = GST_VIDEO_FORMAT_YUY2;
    break;
  default:
    GST_LOG_OBJECT (element, "Pixel format %s is not handled by avfvideosrc",
        [[pixel_format stringValue] UTF8String]);
    break;
  }

  return gst_format;
}

- (BOOL)getDeviceCaps:(GstCaps *)result
{
  NSArray *formats = [device valueForKey:@"formats"];
  NSArray *pixel_formats = output.availableVideoCVPixelFormatTypes;

  GST_DEBUG_OBJECT (element, "Getting device caps");

  /* Do not use AVCaptureDeviceFormat or AVFrameRateRange only
   * available in iOS >= 7.0. We use a dynamic approach with key-value
   * coding or performSelector */
  for (NSObject *f in [formats reverseObjectEnumerator]) {
    CMFormatDescriptionRef formatDescription;
    CMVideoDimensions dimensions;

    /* formatDescription can't be retrieved with valueForKey so use a selector here */
    formatDescription = (CMFormatDescriptionRef) [f performSelector:@selector(formatDescription)];
    dimensions = CMVideoFormatDescriptionGetDimensions(formatDescription);
    for (NSObject *rate in [f valueForKey:@"videoSupportedFrameRateRanges"]) {
      int fps_n, fps_d;
      gdouble max_fps;

      [[rate valueForKey:@"maxFrameRate"] getValue:&max_fps];
      gst_util_double_to_fraction (max_fps, &fps_n, &fps_d);

      for (NSNumber *pixel_format in pixel_formats) {
        GstVideoFormat gst_format = [self getGstVideoFormat:pixel_format];
        if (gst_format != GST_VIDEO_FORMAT_UNKNOWN)
          gst_caps_append (result, GST_AVF_CAPS_NEW (gst_format, dimensions.width, dimensions.height, fps_n, fps_d));
      }
    }
  }
  GST_LOG_OBJECT (element, "Device returned the following caps %" GST_PTR_FORMAT, result);
  return YES;
}

- (BOOL)setDeviceCaps:(GstVideoInfo *)info
{
  double framerate;
  gboolean found_format = FALSE, found_framerate = FALSE;
  NSArray *formats = [device valueForKey:@"formats"];
  gst_util_fraction_to_double (info->fps_n, info->fps_d, &framerate);

  GST_DEBUG_OBJECT (element, "Setting device caps");

  if ([device lockForConfiguration:NULL] == YES) {
    for (NSObject *f in formats) {
      CMFormatDescriptionRef formatDescription;
      CMVideoDimensions dimensions;

      formatDescription = (CMFormatDescriptionRef) [f performSelector:@selector(formatDescription)];
      dimensions = CMVideoFormatDescriptionGetDimensions(formatDescription);
      if (dimensions.width == info->width && dimensions.height == info->height) {
        found_format = TRUE;
        [device setValue:f forKey:@"activeFormat"];
        for (NSObject *rate in [f valueForKey:@"videoSupportedFrameRateRanges"]) {
          gdouble max_frame_rate;

          [[rate valueForKey:@"maxFrameRate"] getValue:&max_frame_rate];
          if (abs (framerate - max_frame_rate) < 0.00001) {
            NSValue *min_frame_duration, *max_frame_duration;

            found_framerate = TRUE;
            min_frame_duration = [rate valueForKey:@"minFrameDuration"];
            max_frame_duration = [rate valueForKey:@"maxFrameDuration"];
            [device setValue:min_frame_duration forKey:@"activeVideoMinFrameDuration"];
            @try {
              /* Only available on OSX >= 10.8 and iOS >= 7.0 */
              [device setValue:max_frame_duration forKey:@"activeVideoMaxFrameDuration"];
            } @catch (NSException *exception) {
              if (![[exception name] isEqualToString:NSUndefinedKeyException]) {
                GST_WARNING ("An unexcepted error occured: %s",
                              [exception.reason UTF8String]);
              }
            }
            break;
          }
        }
      }
    }
    if (!found_format) {
      GST_WARNING ("Unsupported capture dimensions %dx%d", info->width, info->height);
      return NO;
    }
    if (!found_framerate) {
      GST_WARNING ("Unsupported capture framerate %d/%d", info->fps_n, info->fps_d);
      return NO;
    }
  } else {
    GST_WARNING ("Couldn't lock device for configuration");
    return NO;
  }
  return YES;
}

- (BOOL)getSessionPresetCaps:(GstCaps *)result
{
  NSArray *pixel_formats = output.availableVideoCVPixelFormatTypes;
  for (NSNumber *pixel_format in pixel_formats) {
    GstVideoFormat gst_format = [self getGstVideoFormat:pixel_format];
    if (gst_format == GST_VIDEO_FORMAT_UNKNOWN)
      continue;

#if HAVE_IOS
    if ([session canSetSessionPreset:AVCaptureSessionPreset1920x1080])
      gst_caps_append (result, GST_AVF_CAPS_NEW (gst_format, 1920, 1080, DEVICE_FPS_N, DEVICE_FPS_D));
#endif
    if ([session canSetSessionPreset:AVCaptureSessionPreset1280x720])
      gst_caps_append (result, GST_AVF_CAPS_NEW (gst_format, 1280, 720, DEVICE_FPS_N, DEVICE_FPS_D));
    if ([session canSetSessionPreset:AVCaptureSessionPreset640x480])
      gst_caps_append (result, GST_AVF_CAPS_NEW (gst_format, 640, 480, DEVICE_FPS_N, DEVICE_FPS_D));
    if ([session canSetSessionPreset:AVCaptureSessionPresetMedium])
      gst_caps_append (result, GST_AVF_CAPS_NEW (gst_format, 480, 360, DEVICE_FPS_N, DEVICE_FPS_D));
    if ([session canSetSessionPreset:AVCaptureSessionPreset352x288])
      gst_caps_append (result, GST_AVF_CAPS_NEW (gst_format, 352, 288, DEVICE_FPS_N, DEVICE_FPS_D));
    if ([session canSetSessionPreset:AVCaptureSessionPresetLow])
      gst_caps_append (result, GST_AVF_CAPS_NEW (gst_format, 192, 144, DEVICE_FPS_N, DEVICE_FPS_D));
  }

  GST_LOG_OBJECT (element, "Session presets returned the following caps %" GST_PTR_FORMAT, result);

  return YES;
}

- (BOOL)setSessionPresetCaps:(GstVideoInfo *)info;
{
  GST_DEBUG_OBJECT (element, "Setting session presset caps");

  if ([device lockForConfiguration:NULL] != YES) {
    GST_WARNING ("Couldn't lock device for configuration");
    return NO;
  }

  switch (info->width) {
  case 192:
    session.sessionPreset = AVCaptureSessionPresetLow;
    break;
  case 352:
    session.sessionPreset = AVCaptureSessionPreset352x288;
    break;
  case 480:
    session.sessionPreset = AVCaptureSessionPresetMedium;
    break;
  case 640:
    session.sessionPreset = AVCaptureSessionPreset640x480;
    break;
  case 1280:
    session.sessionPreset = AVCaptureSessionPreset1280x720;
    break;
#if HAVE_IOS
  case 1920:
    session.sessionPreset = AVCaptureSessionPreset1920x1080;
    break;
#endif
  default:
    GST_WARNING ("Unsupported capture dimensions %dx%d", info->width, info->height);
    return NO;
  }
  return YES;
}

- (GstCaps *)getCaps
{
  GstCaps *result;
  NSArray *pixel_formats;

  if (session == nil)
    return NULL; /* BaseSrc will return template caps */

  result = gst_caps_new_empty ();
  pixel_formats = output.availableVideoCVPixelFormatTypes;

  if (captureScreen) {
#if !HAVE_IOS
    CGRect rect = CGDisplayBounds (displayId);
    for (NSNumber *pixel_format in pixel_formats) {
      GstVideoFormat gst_format = [self getGstVideoFormat:pixel_format];
      if (gst_format != GST_VIDEO_FORMAT_UNKNOWN)
        gst_caps_append (result, gst_caps_new_simple ("video/x-raw",
            "width", G_TYPE_INT, (int)rect.size.width,
            "height", G_TYPE_INT, (int)rect.size.height,
            "format", G_TYPE_STRING, gst_video_format_to_string (gst_format),
            NULL));
    }
#else
    GST_WARNING ("Screen capture is not supported by iOS");
#endif
    return result;
  }

  @try {

    [self getDeviceCaps:result];

  } @catch (NSException *exception) {

    if (![[exception name] isEqualToString:NSUndefinedKeyException]) {
      GST_WARNING ("An unexcepted error occured: %s", [exception.reason UTF8String]);
      return result;
    }

    /* Fallback on session presets API for iOS < 7.0 */
    [self getSessionPresetCaps:result];
  }

  return result;
}

- (BOOL)setCaps:(GstCaps *)new_caps
{
  GstVideoInfo info;
  BOOL success = YES, *successPtr = &success;

  gst_video_info_init (&info);
  gst_video_info_from_caps (&info, new_caps);

  width = info.width;
  height = info.height;
  format = info.finfo->format;
  latency = gst_util_uint64_scale (GST_SECOND, info.fps_d, info.fps_n);

  dispatch_sync (mainQueue, ^{
    int newformat;

    g_assert (![session isRunning]);

    if (captureScreen) {
#if !HAVE_IOS
      AVCaptureScreenInput *screenInput = (AVCaptureScreenInput *)input;
      screenInput.minFrameDuration = CMTimeMake(info.fps_d, info.fps_n);
#else
      GST_WARNING ("Screen capture is not supported by iOS");
      *successPtr = NO;
      return;
#endif
    } else {
      @try {

        /* formats and activeFormat keys are only available on OSX >= 10.7 and iOS >= 7.0 */
        *successPtr = [self setDeviceCaps:(GstVideoInfo *)&info];
        if (*successPtr != YES)
          return;

      } @catch (NSException *exception) {

        if (![[exception name] isEqualToString:NSUndefinedKeyException]) {
          GST_WARNING ("An unexcepted error occured: %s", [exception.reason UTF8String]);
          *successPtr = NO;
          return;
        }

        /* Fallback on session presets API for iOS < 7.0 */
        *successPtr = [self setSessionPresetCaps:(GstVideoInfo *)&info];
        if (*successPtr != YES)
          return;
      }
    }

    switch (format) {
      case GST_VIDEO_FORMAT_NV12:
        newformat = kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange;
        break;
      case GST_VIDEO_FORMAT_UYVY:
         newformat = kCVPixelFormatType_422YpCbCr8;
        break;
      case GST_VIDEO_FORMAT_YUY2:
         newformat = kCVPixelFormatType_422YpCbCr8_yuvs;
        break;
      case GST_VIDEO_FORMAT_BGRA:
         newformat = kCVPixelFormatType_32BGRA;
        break;
      default:
        *successPtr = NO;
        GST_WARNING ("Unsupported output format %s",
            gst_video_format_to_string (format));
        return;
    }

    GST_DEBUG_OBJECT(element,
       "Width: %d Height: %d Format: %" GST_FOURCC_FORMAT,
       width, height,
       GST_FOURCC_ARGS (gst_video_format_to_fourcc (format)));

    output.videoSettings = [NSDictionary
        dictionaryWithObject:[NSNumber numberWithInt:newformat]
        forKey:(NSString*)kCVPixelBufferPixelFormatTypeKey];

    caps = gst_caps_copy (new_caps);
    [session startRunning];

    /* Unlock device configuration only after session is started so the session
     * won't reset the capture formats */
    [device unlockForConfiguration];
  });

  return success;
}

- (BOOL)start
{
  bufQueueLock = [[NSConditionLock alloc] initWithCondition:NO_BUFFERS];
  bufQueue = [[NSMutableArray alloc] initWithCapacity:BUFFER_QUEUE_SIZE];
  stopRequest = NO;

  offset = 0;
  latency = GST_CLOCK_TIME_NONE;
  startAVFTimestamp = GST_CLOCK_TIME_NONE;
  startTimestamp = GST_CLOCK_TIME_NONE;

  lastSampling = GST_CLOCK_TIME_NONE;
  count = 0;
  fps = -1;

  return YES;
}

- (BOOL)stop
{
  dispatch_sync (mainQueue, ^{ [session stopRunning]; });
  dispatch_sync (workerQueue, ^{});

  [bufQueueLock release];
  bufQueueLock = nil;
  [bufQueue release];
  bufQueue = nil;

  return YES;
}

- (BOOL)query:(GstQuery *)query
{
  BOOL result = NO;

  if (GST_QUERY_TYPE (query) == GST_QUERY_LATENCY) {
    if (device != nil) {
      GstClockTime min_latency, max_latency;

      min_latency = max_latency = latency;
      result = YES;

      GST_DEBUG_OBJECT (element, "reporting latency of min %" GST_TIME_FORMAT
          " max %" GST_TIME_FORMAT,
          GST_TIME_ARGS (min_latency), GST_TIME_ARGS (max_latency));
      gst_query_set_latency (query, TRUE, min_latency, max_latency);
    }
  } else {
    result = GST_BASE_SRC_CLASS (parent_class)->query (baseSrc, query);
  }

  return result;
}

- (BOOL)decideAllocation:(GstQuery *)query
{
  useVideoMeta = gst_query_find_allocation_meta (query,
      GST_VIDEO_META_API_TYPE, NULL);

  return YES;
}

- (BOOL)unlock
{
  [bufQueueLock lock];
  stopRequest = YES;
  [bufQueueLock unlockWithCondition:HAS_BUFFER_OR_STOP_REQUEST];

  return YES;
}

- (BOOL)unlockStop
{
  [bufQueueLock lock];
  stopRequest = NO;
  [bufQueueLock unlock];

  return YES;
}

- (GstStateChangeReturn)changeState:(GstStateChange)transition
{
  GstStateChangeReturn ret;

  if (transition == GST_STATE_CHANGE_NULL_TO_READY) {
    if (![self openDevice])
      return GST_STATE_CHANGE_FAILURE;
  }

  ret = GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);

  if (transition == GST_STATE_CHANGE_READY_TO_NULL)
    [self closeDevice];

  return ret;
}

- (void)captureOutput:(AVCaptureOutput *)captureOutput
didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
       fromConnection:(AVCaptureConnection *)connection
{
  [bufQueueLock lock];

  if (stopRequest) {
    [bufQueueLock unlock];
    return;
  }

  if ([bufQueue count] == BUFFER_QUEUE_SIZE)
    [bufQueue removeLastObject];

  [bufQueue insertObject:(id)sampleBuffer
                 atIndex:0];

  [bufQueueLock unlockWithCondition:HAS_BUFFER_OR_STOP_REQUEST];
}

- (GstFlowReturn)create:(GstBuffer **)buf
{
  CMSampleBufferRef sbuf;
  CVImageBufferRef image_buf;
  CVPixelBufferRef pixel_buf;
  size_t cur_width, cur_height;

  [bufQueueLock lockWhenCondition:HAS_BUFFER_OR_STOP_REQUEST];
  if (stopRequest) {
    [bufQueueLock unlock];
    return GST_FLOW_FLUSHING;
  }

  sbuf = (CMSampleBufferRef) [bufQueue lastObject];
  CFRetain (sbuf);
  [bufQueue removeLastObject];
  [bufQueueLock unlockWithCondition:
      ([bufQueue count] == 0) ? NO_BUFFERS : HAS_BUFFER_OR_STOP_REQUEST];

  /* Check output frame size dimensions */
  image_buf = CMSampleBufferGetImageBuffer (sbuf);
  if (image_buf) {
    pixel_buf = (CVPixelBufferRef) image_buf;
    cur_width = CVPixelBufferGetWidth (pixel_buf);
    cur_height = CVPixelBufferGetHeight (pixel_buf);

    if (width != cur_width || height != cur_height) {
      /* Set new caps according to current frame dimensions */
      GST_WARNING ("Output frame size has changed %dx%d -> %dx%d, updating caps",
          width, height, (int)cur_width, (int)cur_height);
      width = cur_width;
      height = cur_height;
      gst_caps_set_simple (caps,
        "width", G_TYPE_INT, width,
        "height", G_TYPE_INT, height,
        NULL);
      gst_pad_push_event (GST_BASE_SINK_PAD (baseSrc), gst_event_new_caps (caps));
    }
  }

  *buf = gst_core_media_buffer_new (sbuf, useVideoMeta);
  CFRelease (sbuf);

  [self timestampBuffer:*buf sampleBuffer:sbuf];

  if (doStats)
    [self updateStatistics];

  return GST_FLOW_OK;
}

- (void)timestampBuffer:(GstBuffer *)buf
           sampleBuffer:(CMSampleBufferRef)sbuf
{
  CMSampleTimingInfo time_info;
  GstClockTime timestamp, duration;
  CMItemCount num_timings;

  timestamp = GST_CLOCK_TIME_NONE;
  duration = GST_CLOCK_TIME_NONE;
  if (CMSampleBufferGetOutputSampleTimingInfoArray(sbuf, 1, &time_info, &num_timings) == noErr) {
    timestamp = gst_util_uint64_scale (GST_SECOND,
            time_info.presentationTimeStamp.value, time_info.presentationTimeStamp.timescale);
    duration = gst_util_uint64_scale (GST_SECOND,
            time_info.duration.value, time_info.duration.timescale);

    if (offset == 0) {
      GstClock *clock;

      GST_OBJECT_LOCK (element);
      clock = GST_ELEMENT_CLOCK (element);
      if (clock != NULL) {
        startTimestamp = gst_clock_get_time (clock) - element->base_time;
      }
      GST_OBJECT_UNLOCK (element);

      startAVFTimestamp = timestamp;
    }

    if (GST_CLOCK_TIME_IS_VALID (startAVFTimestamp) &&
        GST_CLOCK_TIME_IS_VALID (startTimestamp))
      timestamp = startTimestamp + (timestamp - startAVFTimestamp);
  }

  GST_BUFFER_OFFSET (buf) = offset++;
  GST_BUFFER_OFFSET_END (buf) = GST_BUFFER_OFFSET (buf) + 1;
  GST_BUFFER_TIMESTAMP (buf) = timestamp;
  GST_BUFFER_DURATION (buf) = duration;
}

- (void)updateStatistics
{
  GstClock *clock;

  GST_OBJECT_LOCK (element);
  clock = GST_ELEMENT_CLOCK (element);
  if (clock != NULL)
    gst_object_ref (clock);
  GST_OBJECT_UNLOCK (element);

  if (clock != NULL) {
    GstClockTime now = gst_clock_get_time (clock);
    gst_object_unref (clock);

    count++;

    if (GST_CLOCK_TIME_IS_VALID (lastSampling)) {
      if (now - lastSampling >= GST_SECOND) {
        GST_OBJECT_LOCK (element);
        fps = count;
        GST_OBJECT_UNLOCK (element);

        g_object_notify (G_OBJECT (element), "fps");

        lastSampling = now;
        count = 0;
      }
    } else {
      lastSampling = now;
    }
  }
}

@end

/*
 * Glue code
 */

enum
{
  PROP_0,
  PROP_DEVICE_INDEX,
  PROP_DO_STATS,
  PROP_FPS,
#if !HAVE_IOS
  PROP_CAPTURE_SCREEN,
  PROP_CAPTURE_SCREEN_CURSOR,
  PROP_CAPTURE_SCREEN_MOUSE_CLICKS,
#endif
};


static void gst_avf_video_src_finalize (GObject * obj);
static void gst_avf_video_src_get_property (GObject * object, guint prop_id,
    GValue * value, GParamSpec * pspec);
static void gst_avf_video_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec);
static GstStateChangeReturn gst_avf_video_src_change_state (
    GstElement * element, GstStateChange transition);
static GstCaps * gst_avf_video_src_get_caps (GstBaseSrc * basesrc,
    GstCaps * filter);
static gboolean gst_avf_video_src_set_caps (GstBaseSrc * basesrc,
    GstCaps * caps);
static gboolean gst_avf_video_src_start (GstBaseSrc * basesrc);
static gboolean gst_avf_video_src_stop (GstBaseSrc * basesrc);
static gboolean gst_avf_video_src_query (GstBaseSrc * basesrc,
    GstQuery * query);
static gboolean gst_avf_video_src_decide_allocation (GstBaseSrc * basesrc,
    GstQuery * query);
static gboolean gst_avf_video_src_unlock (GstBaseSrc * basesrc);
static gboolean gst_avf_video_src_unlock_stop (GstBaseSrc * basesrc);
static GstFlowReturn gst_avf_video_src_create (GstPushSrc * pushsrc,
    GstBuffer ** buf);
static gboolean gst_avf_video_src_negotiate (GstBaseSrc * basesrc);


static void
gst_avf_video_src_class_init (GstAVFVideoSrcClass * klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  GstElementClass *gstelement_class = GST_ELEMENT_CLASS (klass);
  GstBaseSrcClass *gstbasesrc_class = GST_BASE_SRC_CLASS (klass);
  GstPushSrcClass *gstpushsrc_class = GST_PUSH_SRC_CLASS (klass);

  gobject_class->finalize = gst_avf_video_src_finalize;
  gobject_class->get_property = gst_avf_video_src_get_property;
  gobject_class->set_property = gst_avf_video_src_set_property;

  gstelement_class->change_state = gst_avf_video_src_change_state;

  gstbasesrc_class->get_caps = gst_avf_video_src_get_caps;
  gstbasesrc_class->set_caps = gst_avf_video_src_set_caps;
  gstbasesrc_class->start = gst_avf_video_src_start;
  gstbasesrc_class->stop = gst_avf_video_src_stop;
  gstbasesrc_class->query = gst_avf_video_src_query;
  gstbasesrc_class->unlock = gst_avf_video_src_unlock;
  gstbasesrc_class->unlock_stop = gst_avf_video_src_unlock_stop;
  gstbasesrc_class->decide_allocation = gst_avf_video_src_decide_allocation;
  gstbasesrc_class->negotiate = gst_avf_video_src_negotiate;

  gstpushsrc_class->create = gst_avf_video_src_create;

  gst_element_class_set_metadata (gstelement_class,
      "Video Source (AVFoundation)", "Source/Video",
      "Reads frames from an iOS AVFoundation device",
      "Ole André Vadla Ravnås <oleavr@soundrop.com>");

  gst_element_class_add_pad_template (gstelement_class,
      gst_static_pad_template_get (&src_template));

  g_object_class_install_property (gobject_class, PROP_DEVICE_INDEX,
      g_param_spec_int ("device-index", "Device Index",
          "The zero-based device index",
          -1, G_MAXINT, DEFAULT_DEVICE_INDEX,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_DO_STATS,
      g_param_spec_boolean ("do-stats", "Enable statistics",
          "Enable logging of statistics", DEFAULT_DO_STATS,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_FPS,
      g_param_spec_int ("fps", "Frames per second",
          "Last measured framerate, if statistics are enabled",
          -1, G_MAXINT, -1, G_PARAM_READABLE | G_PARAM_STATIC_STRINGS));
#if !HAVE_IOS
  g_object_class_install_property (gobject_class, PROP_CAPTURE_SCREEN,
      g_param_spec_boolean ("capture-screen", "Enable screen capture",
          "Enable screen capture functionality", FALSE,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_CAPTURE_SCREEN_CURSOR,
      g_param_spec_boolean ("capture-screen-cursor", "Capture screen cursor",
          "Enable cursor capture while capturing screen", FALSE,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
  g_object_class_install_property (gobject_class, PROP_CAPTURE_SCREEN_MOUSE_CLICKS,
      g_param_spec_boolean ("capture-screen-mouse-clicks", "Enable mouse clicks capture",
          "Enable mouse clicks capture while capturing screen", FALSE,
          G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
#endif

  GST_DEBUG_CATEGORY_INIT (gst_avf_video_src_debug, "avfvideosrc",
      0, "iOS AVFoundation video source");
}

#define OBJC_CALLOUT_BEGIN() \
  NSAutoreleasePool *pool; \
  \
  pool = [[NSAutoreleasePool alloc] init]
#define OBJC_CALLOUT_END() \
  [pool release]


static void
gst_avf_video_src_init (GstAVFVideoSrc * src)
{
  OBJC_CALLOUT_BEGIN ();
  src->impl = [[GstAVFVideoSrcImpl alloc] initWithSrc:GST_PUSH_SRC (src)];
  OBJC_CALLOUT_END ();
}

static void
gst_avf_video_src_finalize (GObject * obj)
{
  OBJC_CALLOUT_BEGIN ();
  [GST_AVF_VIDEO_SRC_IMPL (obj) release];
  OBJC_CALLOUT_END ();

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

static void
gst_avf_video_src_get_property (GObject * object, guint prop_id, GValue * value,
    GParamSpec * pspec)
{
  GstAVFVideoSrcImpl *impl = GST_AVF_VIDEO_SRC_IMPL (object);

  switch (prop_id) {
#if !HAVE_IOS
    case PROP_CAPTURE_SCREEN:
      g_value_set_boolean (value, impl.captureScreen);
      break;
    case PROP_CAPTURE_SCREEN_CURSOR:
      g_value_set_boolean (value, impl.captureScreenCursor);
      break;
    case PROP_CAPTURE_SCREEN_MOUSE_CLICKS:
      g_value_set_boolean (value, impl.captureScreenMouseClicks);
      break;
#endif
    case PROP_DEVICE_INDEX:
      g_value_set_int (value, impl.deviceIndex);
      break;
    case PROP_DO_STATS:
      g_value_set_boolean (value, impl.doStats);
      break;
    case PROP_FPS:
      GST_OBJECT_LOCK (object);
      g_value_set_int (value, impl.fps);
      GST_OBJECT_UNLOCK (object);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_avf_video_src_set_property (GObject * object, guint prop_id,
    const GValue * value, GParamSpec * pspec)
{
  GstAVFVideoSrcImpl *impl = GST_AVF_VIDEO_SRC_IMPL (object);

  switch (prop_id) {
#if !HAVE_IOS
    case PROP_CAPTURE_SCREEN:
      impl.captureScreen = g_value_get_boolean (value);
      break;
    case PROP_CAPTURE_SCREEN_CURSOR:
      impl.captureScreenCursor = g_value_get_boolean (value);
      break;
    case PROP_CAPTURE_SCREEN_MOUSE_CLICKS:
      impl.captureScreenMouseClicks = g_value_get_boolean (value);
      break;
#endif
    case PROP_DEVICE_INDEX:
      impl.deviceIndex = g_value_get_int (value);
      break;
    case PROP_DO_STATS:
      impl.doStats = g_value_get_boolean (value);
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static GstStateChangeReturn
gst_avf_video_src_change_state (GstElement * element, GstStateChange transition)
{
  GstStateChangeReturn ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (element) changeState: transition];
  OBJC_CALLOUT_END ();

  return ret;
}

static GstCaps *
gst_avf_video_src_get_caps (GstBaseSrc * basesrc, GstCaps * filter)
{
  GstCaps *ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) getCaps];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_set_caps (GstBaseSrc * basesrc, GstCaps * caps)
{
  gboolean ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) setCaps:caps];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_start (GstBaseSrc * basesrc)
{
  gboolean ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) start];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_stop (GstBaseSrc * basesrc)
{
  gboolean ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) stop];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_query (GstBaseSrc * basesrc, GstQuery * query)
{
  gboolean ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) query:query];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_decide_allocation (GstBaseSrc * basesrc, GstQuery * query)
{
  gboolean ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) decideAllocation:query];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_unlock (GstBaseSrc * basesrc)
{
  gboolean ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) unlock];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_unlock_stop (GstBaseSrc * basesrc)
{
  gboolean ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (basesrc) unlockStop];
  OBJC_CALLOUT_END ();

  return ret;
}

static GstFlowReturn
gst_avf_video_src_create (GstPushSrc * pushsrc, GstBuffer ** buf)
{
  GstFlowReturn ret;

  OBJC_CALLOUT_BEGIN ();
  ret = [GST_AVF_VIDEO_SRC_IMPL (pushsrc) create: buf];
  OBJC_CALLOUT_END ();

  return ret;
}

static gboolean
gst_avf_video_src_negotiate (GstBaseSrc * basesrc)
{
  /* FIXME: We don't support reconfiguration yet */
  if (gst_pad_has_current_caps (GST_BASE_SRC_PAD (basesrc)))
    return TRUE;

  return GST_BASE_SRC_CLASS (parent_class)->negotiate (basesrc);
}