在Android上创建视频文件

Question

在我的Android应用中,我正在尝试创建视频文件,在视频的给定时间位置添加音轨.我使用了MediaMuxer并改变了presentationTimeUs移动音频的值.但显然这不是要走的路,因为视频的开始时间也会发生变化.另一个问题是mp3音频不起作用.这是我到目前为止的尝试:

final long audioPositionUs = 10000000;
File fileOut = new File (Environment.getExternalStoragePublicDirectory (
  Environment.DIRECTORY_MOVIES) + "/output.mp4");
fileOut.createNewFile ();
MediaExtractor videoExtractor = new MediaExtractor ();
MediaExtractor audioExtractor = new MediaExtractor ();
AssetFileDescriptor videoDescriptor = getAssets ().openFd ("video.mp4");
// AssetFileDescriptor audioDescriptor = getAssets ().openFd ("audio.mp3"); // ?!
AssetFileDescriptor audioDescriptor = getAssets ().openFd ("audio.aac");
videoExtractor.setDataSource (videoDescriptor.getFileDescriptor (),
    videoDescriptor.getStartOffset (), videoDescriptor.getLength ());
audioExtractor.setDataSource (audioDescriptor.getFileDescriptor (),
    audioDescriptor.getStartOffset (), audioDescriptor.getLength ());
MediaFormat videoFormat = null;
for (int i = 0; i < videoExtractor.getTrackCount (); i++) {
  if (videoExtractor.getTrackFormat (i).getString (
      MediaFormat.KEY_MIME).startsWith ("video/")) {
    videoExtractor.selectTrack (i);
    videoFormat = videoExtractor.getTrackFormat (i);
    break;
  }
}
audioExtractor.selectTrack (0);
MediaFormat audioFormat = audioExtractor.getTrackFormat (0);
MediaMuxer muxer = new MediaMuxer (fileOut.getAbsolutePath (),
    MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
int videoTrack = muxer.addTrack (videoFormat);
int audioTrack = muxer.addTrack (audioFormat);
boolean end = false;
int sampleSize = 256 * 1024;
ByteBuffer videoBuffer = ByteBuffer.allocate (sampleSize);
ByteBuffer audioBuffer = ByteBuffer.allocate (sampleSize);
MediaCodec.BufferInfo videoBufferInfo = new MediaCodec.BufferInfo ();
MediaCodec.BufferInfo audioBufferInfo = new MediaCodec.BufferInfo ();
videoExtractor.seekTo (0, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
audioExtractor.seekTo (0, MediaExtractor.SEEK_TO_CLOSEST_SYNC);
muxer.start ();
while (!end) {
  videoBufferInfo.size = videoExtractor.readSampleData (videoBuffer, 0);
  if (videoBufferInfo.size < 0) {
    end = true;
    videoBufferInfo.size = 0;
  } else {
    videoBufferInfo.presentationTimeUs = videoExtractor.getSampleTime ();
    videoBufferInfo.flags = videoExtractor.getSampleFlags ();
    muxer.writeSampleData (videoTrack, videoBuffer, videoBufferInfo);
    videoExtractor.advance ();
  }
}
end = false;
while (!end) {
  audioBufferInfo.size = audioExtractor.readSampleData (audioBuffer, 0);
  if (audioBufferInfo.size < 0) {
    end = true;
    audioBufferInfo.size = 0;
  } else {
    audioBufferInfo.presentationTimeUs = audioExtractor.getSampleTime () +
        audioPositionUs;
    audioBufferInfo.flags = audioExtractor.getSampleFlags ();
    muxer.writeSampleData (audioTrack, audioBuffer, audioBufferInfo);
    audioExtractor.advance ();
  }
}
muxer.stop ();
muxer.release ();

您能否详细说明(以及代码,如果可能的话)来帮我解决这个问题？

Answer 1

作为解决方法，您可以通过用无声轨道填充音轨头部来创建临时音轨，然后将其与addTrack.

PS：我原以为presentationTimeUs应该也可以。

PS2：也许set的方法MediaCodec.BufferInfo可能有帮助。