使用 AVCaptureMovieFileOutput 保存视频后不播放音频

Question

我尝试使用以下代码保存来自 iphone 相机的视频文件：

class Camera {

...

private func loadDeviceInput() {
    let devices = AVCaptureDevice.devices() as! [AVCaptureDevice]
    for device in devices {
        if device.hasMediaType(AVMediaTypeVideo) {
            if device.position == .Back {
                _deviceBack = device
                _inputBack  = try? AVCaptureDeviceInput(device: device)
            }
            else if device.position == .Front {
                _deviceFront = device
                _inputFront  = try? AVCaptureDeviceInput(device: device)
            }
        }
        else if device.hasMediaType(AVMediaTypeAudio) {
            _inputAudio = try? AVCaptureDeviceInput(device: device)
        }
    }
}

private func loadDeviceOutput() {
    _outputStill = AVCaptureStillImageOutput()
    _outputStill?.outputSettings = [AVVideoCodecKey: AVVideoCodecJPEG]
    if _session.canAddOutput(_outputStill) {
        _session.addOutput(_outputStill)
    }

    _outputAudio = AVCaptureAudioDataOutput()
    if _session.canAddOutput(_outputAudio) {
        _session.addOutput(_outputAudio)
    }

    _outputVideo = AVCaptureMovieFileOutput()
    _outputVideo?.movieFragmentInterval = CMTimeMake(1, 1) // Save file header every second

    if _session.canAddOutput(_outputVideo) {
        _session.addOutput(_outputVideo)
    }
}

func startVideoCapture(writeTo file: NSURL, startedBlock: JrmgxNSURLResultBlock, stopedBlock: JrmgxNSURLResultBlock) {
    isSessionRunning()

    prepareForVideoCapture()
    _startVideoCaptureBlock = startedBlock
    _stopVideoCaptureBlock  = stopedBlock

    if _outputVideo?.connectionWithMediaType(AVMediaTypeVideo)?.active ?? false == true {
        _outputVideo?.startRecordingToOutputFileURL(file, recordingDelegate: self)
    }
    else {
        // ERROR
    }
}

...
}

到目前为止，这是可行的，但是当我使用 AVPlayer 播放视频时，没有播放声音。如果我用 Quiktime 尝试视频，同样的问题，没有声音。但是当我用 VLC 打开它时，声音就会播放。

作为参考，这是我播放视频的方式，它运行但没有声音：

player = AVPlayer(URL: v)
player.actionAtItemEnd = .None
player.muted = false
player.volume = 1
player.play()

我用ffprone检查了视频：

$ ffprobe test4.mp4 
ffprobe version 2.8.1
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test4.mp4':
  Metadata:
    major_brand     : qt  
    minor_version   : 0
    compatible_brands: qt  
    creation_time   : 2016-01-21 13:13:55
  Duration: 00:00:06.37, start: 0.000000, bitrate: 818 kb/s
    Stream #0:0(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(tv, smpte170m/bt709/bt709), 480x360, 741 kb/s, 30.01 fps, 30 tbr, 600 tbn, 1200 tbc (default)
    Metadata:
      rotate          : 90
      creation_time   : 2016-01-21 13:13:55
      handler_name    : Core Media Video
    Side data:
      displaymatrix: rotation of -90.00 degrees
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 62 kb/s (default)
    Metadata:
      creation_time   : 2016-01-21 13:13:55
      handler_name    : Core Media Audio

我不知道出了什么问题， 你能帮帮我吗？

谢谢

Answer 1

mp4 和 mov 文件非常相似，但有细微差别。我认为 VLC 只是意识到该文件实际上是一个 .mov 然后相应地播放它，但 AVPlayer 并没有接受它。

您正在使用 AVCaptureMovieFileOutput 保存视频及其文档状态：

AVCaptureMovieFileOutput is a concrete sub-class of AVCaptureFileOutput you use to capture data to a QuickTime movie.

对 QuickTime 电影的一些研究表明，它的标准文件扩展名是 .mov：

Save as QuickTime movie – This option will save the embedded video in a *.mov file format no matter what the original container is/was.

如果您将文件保存为 .mov，则应该不会再出现问题了。