Get subtitles from video (avi, mp4, mkv etc.)

Question

Is it possible to get subtitles from popular video file formats (*.mp4, *.mkv, *.avi etc.) using some library or API to third-party software? Preferable language is Java, but this is not a requirement.

Answer 1

Recently I am study on ffmpeg you can find some information from here. As far as I know ffmpeg can extract the subtitles as a txt stream of a video file. But I not sure if it difficult to use ffmpeg to meet your requirement. I just take a look at the file ffplay.c which you can find in the ffmpeg open source codes. I found some codes as follows

switch(avctx->codec_type){
    case avmedia_type_audio:
        is->last_audio_stream = stream_index; 
        if(audio_codec_name) 
            codec = avcodec_find_decoder_by_name(audio_codec_name); 
        break;
    case avmedia_type_subtitle:
        is->last_subtitle_stream = stream_index; 
        if(subtitle_codec_name) 
           codec = avcodec_find_decoder_by_name(subtitle_codec_name); 
        break;
    case avmedia_type_video: 
        is->last_video_stream = stream_index; 
        if(video_codec_name) 
            codec = avcodec_find_decoder_by_name(video_codec_name); 
        break;
}

and grep 'subtitle' in the file ffplay.c, you'll find more information.

Hope it helps, hope ffmpeg do the help.