51207635: kVTCompressionPropertyKey_DataRateLimits omits B frames

[openradar-mirror]

Description

Summary:

When using the kVTCompressionPropertyKey_DataRateLimits setting with AVVideoCodecTypeH264 and AVVideoProfileLevelH264High41, the resulting output does not include B frames. Compare with AVVideoAverageBitRateKey, which does.

Steps to Reproduce:

See attached code.

Verify B-frame count with the following command:

ffprobe -v error -show_frames $FILE | grep pict_type=B | wc -l

Expected Results:

File contains B-frames.

Actual Results:

File does not contain B-frames.

Version/Build:

iOS 12.3

Configuration:

N/A

---

• (void)test { NSArray *const bitRates = @[ @(3e6), ];

  NSArray *const urls = @[ [[NSBundle bundleForClass:[self class]] URLForResource:@"file" withExtension:@"mp4"], ];

  NSArray *const keyFrameIntervals = @[ @(0.f), ];

  for (NSURL url in urls) { for (NSNumber bitRate in bitRates) { for (NSNumber keyFrameInterval in keyFrameIntervals) { for (NSNumber drl in @[@1, @2, @3]) { [self testUrl:url bitRate:[bitRate floatValue] keyFrameInterval:[keyFrameInterval integerValue] drl:[drl integerValue]]; } } } } }

• (void)testUrl:(NSURL *)url bitRate:(CGFloat)bitRate keyFrameInterval:(NSInteger)keyFrameInterval drl:(NSInteger)drl {

  NSString *extension = nil; if (drl == 1) { extension = @"avg"; } else if (drl == 2) { extension = @"drl"; } else if (drl == 3) { extension = @"both"; }

  NSString *filename = [NSString stringWithFormat:@"test-%@-%ld-bps-%ld-s-%@", [[url URLByDeletingPathExtension] lastPathComponent], (long)bitRate, (long)keyFrameInterval, extension];

  NSURL *const outputUrl = [[[NSURL fileURLWithPath:NSTemporaryDirectory()] URLByAppendingPathComponent:filename] URLByAppendingPathExtension:@"mp4"];

  if ([[NSFileManager defaultManager]fileExistsAtPath:outputUrl.path]) { [[NSFileManager defaultManager] removeItemAtURL:outputUrl error:nil]; }

  AVAsset const asset = [AVAsset assetWithURL:url]; AVAssetTrack const videoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] firstObject]; NSError error = nil; AVAssetReader const assetReader = [AVAssetReader assetReaderWithAsset:asset error:&error]; XCTAssertNil(error); AVAssetWriter *const assetWriter = [AVAssetWriter assetWriterWithURL:outputUrl fileType:AVFileTypeMPEG4 error:&error]; XCTAssertNil(error);

  NSMutableDictionary *const compressionProperties = [NSMutableDictionary new]; compressionProperties[AVVideoProfileLevelKey] = AVVideoProfileLevelH264High41; compressionProperties[AVVideoMaxKeyFrameIntervalDurationKey] = @(keyFrameInterval);

  if (drl == 1 || drl == 3) { compressionProperties[AVVideoAverageBitRateKey] = @(bitRate); } else if (drl == 2 || drl == 3) { compressionProperties[(id)kVTCompressionPropertyKey_DataRateLimits] = @[@(bitRate / 8.f), @1]; }

  AVAssetWriterInput *const input = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeVideo outputSettings:@{ AVVideoCodecKey: AVVideoCodecTypeH264, AVVideoWidthKey: @(videoTrack.naturalSize.width), AVVideoHeightKey: @(videoTrack.naturalSize.height), AVVideoCompressionPropertiesKey: compressionProperties }];

  AVAssetReaderOutput *const output = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:@{ (id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_32BGRA), }];

  [assetReader addOutput:output]; [assetWriter addInput:input];

  XCTAssertNil(assetReader.error); XCTAssertNil(assetWriter.error);

  [assetReader startReading]; [assetWriter startWriting];

  [assetWriter startSessionAtSourceTime:kCMTimeZero];

  const dispatch_queue_t queue = dispatch_queue_create("transcode", DISPATCH_QUEUE_SERIAL); const dispatch_semaphore_t transcode = dispatch_semaphore_create(0); [input requestMediaDataWhenReadyOnQueue:queue usingBlock:^{ while ([input isReadyForMoreMediaData]) { const CMSampleBufferRef sampleBuffer = [output copyNextSampleBuffer];

      XCTAssertNil(assetReader.error);
      XCTAssertNil(assetWriter.error);
  
      if (sampleBuffer) {
          [input appendSampleBuffer:sampleBuffer];
          CFRelease(sampleBuffer);
      } else {
          [input markAsFinished];
          dispatch_semaphore_signal(transcode);
      }
  }

  }];

  dispatch_semaphore_wait(transcode, DISPATCH_TIME_FOREVER);

  const dispatch_semaphore_t write = dispatch_semaphore_create(0); [assetWriter finishWritingWithCompletionHandler:^{ dispatch_semaphore_signal(write); }];

  XCTAssertNil(assetWriter.error);

  dispatch_semaphore_wait(write, DISPATCH_TIME_FOREVER);

  NSLog(@"Wrote to %@", outputUrl); }

• Product Version: Created: 2019-05-29T04:08:28.628103 Originated: 2019-05-28T00:00:00 Open Radar Link: http://www.openradar.me/51207635