AVAssetsWriter帧速率

Question

我使用了后续代码对包含多个本地图片的视频进行编码。但问题是我有30张图片，而且只能获得1秒的视频，有没有办法以30秒和24帧速率获取视频？

- (BOOL)encodeReadySamplesFromOutput:(AVAssetReaderOutput *)output toInput:(AVAssetWriterInput *)input
{
    NSLog(@"Frame init m == %d",m);
    while (input.isReadyForMoreMediaData)
    {
        CMSampleBufferRef sampleBuffer = [output copyNextSampleBuffer];
        if (sampleBuffer)
        {
            BOOL handled = NO;
            BOOL error = NO;

            CMItemCount count;
            CMSampleBufferGetSampleTimingInfoArray(sampleBuffer, 0, nil, &count);
            CMSampleTimingInfo *timingInfo = malloc(sizeof(CMSampleTimingInfo) * count);
            CMSampleBufferGetSampleTimingInfoArray(sampleBuffer, count, timingInfo, &count);

            for (CMItemCount i = 0; i < count; i++)
            {
                timingInfo[i].decodeTimeStamp = kCMTimeInvalid;
                timingInfo[i].presentationTimeStamp = CMTimeMake(m, 24);
//                timingInfo[i].duration = CMTimeMake(1, 12);
            }

            CMSampleBufferRef completedSampleBuffer;
            CMSampleBufferCreateCopyWithNewTiming(kCFAllocatorDefault, sampleBuffer, count, timingInfo, &completedSampleBuffer);
            free(timingInfo);

            if (self.reader.status != AVAssetReaderStatusReading || self.writer.status != AVAssetWriterStatusWriting)
            {
                handled = YES;
                error = YES;
            }

            if (!handled && self.videoOutput == output)
            {
                // update the video progress
                ++m;

                NSLog(@"Frame m == %d",m);
                lastSamplePresentationTime = CMSampleBufferGetPresentationTimeStamp(completedSampleBuffer);
                CMTimeValue value = lastSamplePresentationTime.value;
                CMTimeScale scale = lastSamplePresentationTime.timescale;

                NSLog(@"Frame value == %lld", value);
                NSLog(@"Frame scale == %d",scale);
                self.progress = duration == 0 ? 1 : CMTimeGetSeconds(lastSamplePresentationTime) / duration;

                if ([self.delegate respondsToSelector:@selector(exportSession:renderFrame:withPresentationTime:toBuffer:)])
                {
                    CVPixelBufferRef pixelBuffer = (CVPixelBufferRef)CMSampleBufferGetImageBuffer(completedSampleBuffer);
                    CVPixelBufferRef renderBuffer = NULL;
                    CVPixelBufferPoolCreatePixelBuffer(NULL, self.videoPixelBufferAdaptor.pixelBufferPool, &renderBuffer);
                    [self.delegate exportSession:self renderFrame:pixelBuffer withPresentationTime:lastSamplePresentationTime toBuffer:renderBuffer];
                    if (![self.videoPixelBufferAdaptor appendPixelBuffer:renderBuffer withPresentationTime:lastSamplePresentationTime])
                    {
                        error = YES;
                    }
                    CVPixelBufferRelease(renderBuffer);
                    handled = YES;
                }
            }
            if (!handled && ![input appendSampleBuffer:completedSampleBuffer])
            {
                error = YES;
            }
            CFRelease(sampleBuffer);
            CFRelease(completedSampleBuffer);
            if (error)
            {
                return NO;
            }
        }
        else
        {
            [input markAsFinished];
            return NO;
        }
    }
    return YES;
}

Answer 1

除非你得到更多的照片或重复你的照片，否则不会。

在任何一种情况下，您都必须自己计算演示时间，例如CMTimeMake(m, 24)，例如：

[self.videoPixelBufferAdaptor appendPixelBuffer:renderBuffer withPresentationTime:CMTimeMake(m, 24)];

如果您放弃了24fps的要求（为什么还需要？），您可以使用CMTimeMake(m, 1)代替appendPixelBuffer:withPresentationTime:，以1fps的速度获得30张30秒的视频。