Bdtjtk

I'm trying to extract audio from video. This code works well:

ffmpeg('1.mp4').output('1.mp3')

.noVideo()

.format('mp3')

.outputOptions('-ab','192k')

.run();

But if I read the file with a stream like this:

var video = fs.createReadStream('1.mp4');

var audio = fs.createWriteStream('1.mp3');

ffmpeg(video).output(audio)

.noVideo()

.format('mp3')

.outputOptions('-ab','192k')

.run();

The output file weighs 1KB and does not have anything in it.

How can I extract audio using streams?

For further investigation, I added a callback for different sort of errors while transcoding, as well as other events. First hint was the following callback on progress event:

{ frames: NaN,

  currentFps: NaN,

  currentKbps: NaN,

  targetSize: 0,

  timemark: '00:00:00.00' }

As well, there was a stderr event:

ffmpeg version n4.1 Copyright (c) 2000-2018 the FFmpeg developers

  built with gcc 8.2.1 (GCC) 20180831

  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libdrm --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libjack --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-nvdec --enable-nvenc --enable-omx --enable-shared --enable-version3

  libavutil      56. 22.100 / 56. 22.100

  libavcodec     58. 35.100 / 58. 35.100

  libavformat    58. 20.100 / 58. 20.100

  libavdevice    58.  5.100 / 58.  5.100

  libavfilter     7. 40.101 /  7. 40.101

  libswscale      5.  3.100 /  5.  3.100

  libswresample   3.  3.100 /  3.  3.100

  libpostproc    55.  3.100 / 55.  3.100

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x562c9e18de80] stream 0, offset 0x30: partial file

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x562c9e18de80] Could not find codec parameters for stream 0 (Video: h264 (avc1 / 0x31637661), none, 240x180, 374 kb/s): unspecified pixel format

Consider increasing the value for the 'analyzeduration' and 'probesize' options

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'pipe:0':

  Metadata:

    major_brand     : isom

    minor_version   : 512

    compatible_brands: isomiso2avc1mp41

    encoder         : Lavf54.63.104

  Duration: 00:00:14.72, start: 0.000000, bitrate: N/A

    Stream #0:0(und): Video: h264 (avc1 / 0x31637661), none, 240x180, 374 kb/s, 25 fps, 25 tbr, 12800 tbn, 25600 tbc (default)

    Metadata:

      handler_name    : VideoHandler

    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 75 kb/s (default)

    Metadata:

      handler_name    : SoundHandler

Stream mapping:

  Stream #0:1 -> #0:0 (aac (native) -> mp3 (libmp3lame))

[mov,mp4,m4a,3gp,3g2,mj2 @ 0x562c9e18de80] stream 1, offset 0xa1e: partial file

pipe:0: Invalid data found when processing input

Output #0, mp3, to 'pipe:1':

  Metadata:

    major_brand     : isom

    minor_version   : 512

    compatible_brands: isomiso2avc1mp41

    TSSE            : Lavf58.20.100

    Stream #0:0(und): Audio: mp3 (libmp3lame), 44100 Hz, stereo, fltp, 192 kb/s (default)

    Metadata:

      handler_name    : SoundHandler

      encoder         : Lavc58.35.100 libmp3lame

size=       0kB time=00:00:00.00 bitrate=N/A speed=   0x    

{ frames: NaN,

  currentFps: NaN,

  currentKbps: NaN,

  targetSize: 0,

  timemark: '00:00:00.00' }

video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown

Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)

The latter explains the empty file you're seeing in the output. As to why the error only happens while streaming the file, and not while opening it through another method, this answer explains the details: https://stackoverflow.com/a/40028894/1494833

Unfortunately the library doesn't yet support movflags input option as recommended above (https://github.com/fluent-ffmpeg/node-fluent-ffmpeg/issues/823).

Assuming that you are using the ffmpeg package which is basically a wrapper for running ffmpeg in node, you would have to do it somewhat like this:

This code works on my system using the same file you provided in the comments above but you may have to make some changes (Node v8.12.0, ffmpeg v0.0.4).

const ffmpeg = require('ffmpeg');



try {

    let process = new ffmpeg('3.mp4');

    process.then(function (video) {

        // Callback mode

        video.fnExtractSoundToMP3('3.mp3', function (error, file) {

            if (!error)

                console.log('Audio file: ' + file);

        });

    }, function (err) {

        console.log('Error: ' + err);

    });

} catch (e) {

    console.log(e.code);

    console.log(e.msg);

}