Encoding with HEVC creates excessively large first frame

Originator:cellsworth
Number:rdar://47395179 Date Originated:1/18/2019
Status:Open Resolved:
Product:AVFoundation Product Version:iOS 12.1
Classification: Reproducible:Always
 
The first frame in a AVAssetWriter session using the HEVC codec is excessively large, unless kVTCompressionPropertyKey_DataRateLimits is set.

- (void)testHEVC {
    NSURL *const outputUrl = [[[NSURL fileURLWithPath:NSTemporaryDirectory()]
                               URLByAppendingPathComponent:[[NSUUID UUID] UUIDString]]
                              URLByAppendingPathExtension:@"mp4"];
    NSURL *const url = [[NSBundle bundleForClass:[self class]] URLForResource:@"test-video" withExtension:@"mov"];
    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);

    NSInteger bitRate = 2.5e6;
    AVAssetWriterInput *const input = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeVideo
                                                                     outputSettings:@{
                                                                                      AVVideoCodecKey: AVVideoCodecTypeHEVC,
                                                                                      AVVideoWidthKey: @(1280),
                                                                                      AVVideoHeightKey: @(720),
                                                                                      AVVideoCompressionPropertiesKey: @{
                                                                                              AVVideoAverageBitRateKey: @(bitRate),
                                                                                              // (NSString *)kVTCompressionPropertyKey_DataRateLimits: @[@(bitRate * 5.f / 8.f), @5]
                                                                                              }
                                                                                      }];

    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);
}

Comments


Please note: Reports posted here will not necessarily be seen by Apple. All problems should be submitted at bugreport.apple.com before they are posted here. Please only post information for Radars that you have filed yourself, and please do not include Apple confidential information in your posts. Thank you!