How to combine audio and video?

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keshav poojari 2018-12-10

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https://ww2.mathworks.cn/matlabcentral/answers/434844-how-to-combine-audio-and-video

评论： Walter Roberson 2019-2-24

it will run.. but not play the video... please tell me what the problem and how to resolve that?

videoFReader = vision.VideoFileReader('video1.avi');
[AUDIO,Fs] = audioread('audio1.wav');
videoFWriter = vision.VideoFileWriter('newvideo.avi','AudioInputPort',true);
videoFrame = step(videoFReader);
step(videoFWriter,videoFrame,AUDIO);
release(videoFReader);
release(videoFWriter);

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采纳的回答

Walter Roberson 2018-12-10

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https://ww2.mathworks.cn/matlabcentral/answers/434844-how-to-combine-audio-and-video#answer_351428

You are writing all of the audio for the first frame and only reading and writing one frame.

you need to loop reading one input frame and writing that frame out together with the audio that matches it. For example if your audio output rate were 44100 and your video output were 22 frames per second then you should emit roughly 2000 audio samples for each video frame .

You might want to buffer() your audio to make it easier to write the appropriate amount of audio per frame .

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Walter Roberson 2018-12-12

在 MATLAB Online 中打开

video_filename = 'video1.avi';
audio_filename = 'audio1.wav';
out_filename = 'newvideo.avi';
info = aviinfo(video_filename);
FR = info.FramesPerSecond;
videoFReader = vision.VideoFileReader(audio_filename);
[AUDIO,Fs] = audioread(filename);
SamplesPerFrame = floor(Fs/FR);
videoFWriter = vision.VideoFileWriter(out_filename, 'AudioInputPort', true, 'FrameRate', FR);
framenum = 0;
while ~isDone(videoFReader)
   videoFrame = step(videoFReader);
   this_audio = AUDIO(framenum*SamplesPerFrame + 1 : min(end, (framenum+1)*SamplesPerFrame), :);
   step(videoFWriter,videoFrame, this_audio);
   framenum = framenum + 1;
end
release(videoFReader);
release(videoFWriter);

Note: with this code it would be common for the last few samples of the audio to not be written. This is due to the fact that the audio sampling rate will not typically be an exact multiple of the video frame rate, but the code allocates a fixed number of samples per video frame. For example if the audio is 22100 samples per second and the video is 24 frames per second, that should be an average of 920.833333333333 audio samples per video frame. The code takes the floor, 920 samples per video frame. You can see that after 100 video frames (about 4 seconds) it would be about 83 audio samples behind. You would need to improve the algorithm for selecting out of AUDIO in order to get around this problem.

... ideally you should also take into account that video might be variable frame rate.

Walter Roberson 2018-12-21

编辑：Walter Roberson 2018-12-21

在 MATLAB Online 中打开

Corrected code:

video_filename = 'video1.avi';
audio_filename = 'audio1.wav';
out_filename = 'newvideo.avi';
videoFReader = VideoReader(video_filename);
FR = videoFReader.FrameRate;
[AUDIO,Fs] = audioread(audio_filename);
SamplesPerFrame = floor(Fs/FR);
videoFWriter = vision.VideoFileWriter(out_filename, 'AudioInputPort', true, 'FrameRate', FR);
framenum = 0;
while hasFrame(videoFReader)
   videoFrame = readFrame(videoFReader);
   this_audio = AUDIO(framenum*SamplesPerFrame + 1 : min(end, (framenum+1)*SamplesPerFrame), :);
   if size(this_audio,1) < SamplesPerFrame
       this_audio(SamplesPerFrame,:) = 0; %zero pad short frames
   end
   step(videoFWriter,videoFrame, this_audio);
   framenum = framenum + 1;
end
delete(videoFReader);
release(videoFWriter);

However, my experiments are having a bit of difficulty in playing the result on Mac. aviinfo() says there is incorrect CHUNK information. Apple Quicktime did not include the sound when playing it. But VLC had no problem.

I notice that vision.VideoFileReader() reads the audio in 'native' format -- int16 rather than the floating point that audioreader() automatically converts to.

keshav poojari 2019-2-24

When i used above code to combine audio and video, The output video take much Storage space... can i compress this??? How??

Walter Roberson 2019-2-24

keshav poojari, you might need to post-process the video.

But have a look at the description of the AudioCompressor and VideoCompressor properties that you can set for vision.VideoFileWriter. The choices depend upon what you have installed on your system, so I cannot tell you what the choices are.

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