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• Transcoding Videos Using FastAPI and ffmpeg

  15 janvier 2024, par Sanji Vinsmoke

  I created an API using Fast API where I upload one or more videos, may specify the resolution of transcoding, and the output is transcoded video from 240p upto the resolution I specified. Available resolutions are - 240p, 360p, 480p, 720p, 1080p. I used ffmpeg for the transcoding job.

  


  The problem that is bugging me since yesterday is that, after deploying to the s3 bucket and adding the url for the index.m3u8 file in any hls player, the video is blank. Only the audio and streaming are working. I have tried tweaking with the parameters in the ffmpeg parameters, the error is still there. I tried manually transcoding a video file locally, even that video's index.m3u8 file is blank in live version. I added the relevant codes for this project. I implemented each feature one by one, but I simply cannot find the reason why the video is totally blank on live.

  


  def transcode_video(input_path, output_folder, res, video_id, video_resolution, progress_bar=None):
    # Transcode the video into .m3u8 format with segment format
    output_path = os.path.join(output_folder, f"{res}_{video_id}.m3u8")

    # Use subprocess for command execution
    chunk_size = 1 # Specify the desired chunk size in seconds

    transcode_command = [
        "ffmpeg", "-i", input_path, "-vf", f"scale={res}:'trunc(ow/a/2)*2'", "-c:a", "aac", "-strict", "-2",
        "-f", "segment", "-segment_time", str(chunk_size), "-segment_list", output_path, "-segment_format", "ts",
        f"{output_path.replace('.m3u8', '_%03d.ts')}"
    ]

    try:
        subprocess.run(transcode_command, check=True, capture_output=True)
    except subprocess.CalledProcessError as e:
        print(f"Error during transcoding: {e}")
        print(f"FFmpeg error output: {e.stderr}")
        # Continue with the next video even if an error occurs
        return False

    # Update the progress bar
    if progress_bar:
        progress_bar.update(1)
    return True


def get_bandwidth(resolution):
    # Define a simple function to calculate bandwidth based on resolution
    resolutions_and_bandwidths = {
        240: 400000,
        360: 850000,
        480: 1400000,
        720: 2500000,
        1080: 4500000,
    }
    
    return resolutions_and_bandwidths.get(resolution, 0)
def create_index_m3u8(video_id, resolutions_to_transcode):
    # Write the index.m3u8 file
    index_m3u8_path = os.path.join(OUTPUT_FOLDER, f"index_{video_id}.m3u8")
    with open(index_m3u8_path, "w") as index_file:
        index_file.write("#EXTM3U\n")
        index_file.write("#EXT-X-VERSION:3\n")

        for res in resolutions_to_transcode:
            aspect_ratio = 16 / 9
            folder_name = f"{res}p_{video_id}"
            resolution_file_name = f"{res}_{video_id}.m3u8"
            index_file.write(
                f"#EXT-X-STREAM-INF:BANDWIDTH={get_bandwidth(res)},RESOLUTION={int(res * aspect_ratio)}x{res}\n{folder_name}/{resolution_file_name}\n"
            )


  


  I tried reducing or increasing chunk size, adding codecs, setting up dimensions. Where am I doing wrong ?

  


  My python version is 3.8.18, ffmpeg version-4.4.4, ffmpeg-python version-0.2.0

  


• Why ffmpeg launched on a google cloud function can throw "Error : Output stream error : Maximum call stack size exceeded" ?

  15 décembre 2020, par Stepan Shilin

  I'm trying to process video files with ffmpeg running on google cloud functions. Video files are downloaded from a google file storage, processed in stream by fluent-ffmpeg and streamed to a new google storage file. It works on smaller files but throws an "Output stream error : Maximum call stack size exceeded" on larger files.

  



  I tried running the code on a normal pc, and I haven't encountered this error, even with larger files.

  



  These are the parameters I deploy the function with

  



  gcloud functions deploy $FUNCTION_NAME --runtime nodejs8 --trigger-http --timeout=180 --memory 256


  



  This is the code that processes video

  



  function cutVideo({videoUrl, startTime, duration, dist}) {
    return ffmpeg(videoUrl)
    .outputOptions('-movflags frag_keyframe+empty_moov')
    .videoCodec('copy')
    .audioCodec('copy')
    .format('mp4')
    .setStartTime(startTime)
    .setDuration(duration);
}

const sectionStream = cutVideo({
    videoUrl,
    startTime,
    duration,
    dist: tempFilePath,
});

const outputStream = bucket.file(sectionPath)
.createWriteStream({
    metadata: {
        contentType: config.contentType,
    },
    public: true,
});


  



  Actual error stack looks like this

  



    Error: Output stream error: Maximum call stack size exceeded&#xA;                                                                  at Pumpify.<anonymous> (/srv/node_modules/fluent-ffmpeg/lib/processor.js:498:34)&#xA;                                                                  at emitOne (events.js:121:20)&#xA;                                                                  at Pumpify.emit (events.js:211:7)&#xA;                                                                  at Pumpify.Duplexify._destroy (/srv/node_modules/duplexify/index.js:191:15)&#xA;                                                                  at /srv/node_modules/duplexify/index.js:182:10&#xA;                                                                  at _combinedTickCallback (internal/process/next_tick.js:132:7)&#xA;                                                                  at process._tickDomainCallback (internal/process/next_tick.js:219:9)&#xA;  RangeError: Maximum call stack size exceeded&#xA;                                                                  at replaceProjectIdToken (/srv/node_modules/@google-cloud/projectify/build/src/index.js:28:31)&#xA;                                                                  at replaceProjectIdToken (/srv/node_modules/@google-cloud/projectify/build/src/index.js:37:30)&#xA;                                                                  at replaceProjectIdToken (/srv/node_modules/@google-cloud/projectify/build/src/index.js:37:30)&#xA;                                                                  at value.map.v (/srv/node_modules/@google-cloud/projectify/build/src/index.js:30:32)&#xA;                                                                  at Array.map (<anonymous>)&#xA;                                                                  at replaceProjectIdToken (/srv/node_modules/@google-cloud/projectify/build/src/index.js:30:23)&#xA;                                                                  at replaceProjectIdToken (/srv/node_modules/@google-cloud/projectify/build/src/index.js:37:30)&#xA;                                                                  at replaceProjectIdToken (/srv/node_modules/@google-cloud/projectify/build/src/index.js:37:30)&#xA;                                                                  at value.map.v (/srv/node_modules/@google-cloud/projectify/build/src/index.js:30:32)&#xA;                                                                  at Array.map (<anonymous>)&#xA;</anonymous></anonymous></anonymous>

  



  What could cause this error on a google cloud function ?

  


• FFMPEG Encoding a video from a Readable stream

  4 novembre 2022, par Michael Aubry

  I'm facing an issue with the seeked event in Chrome. The issue seems to be due to how the video being seeked is encoded.

  


  The problem seems to occur most frequently when using ytdl-core and piping a Readable stream into an FFMPEG child process.

  


  let videoStream: Readable = ytdl.downloadFromInfo(info, {
  ...options,
  quality: "highestvideo"
});


  


  With ytdl-core in order to get the highest quality you must combine the audio and video. So here is how I am doing it.

  


  const ytmux = (link, options: any = {}) => {
  const result = new stream.PassThrough({
    highWaterMark: options.highWaterMark || 1024 * 512
  });

  ytdl.getInfo(link, options).then((info: videoInfo) => {
    let audioStream: Readable = ytdl.downloadFromInfo(info, {
      ...options,
      quality: "highestaudio"
    });
    let videoStream: Readable = ytdl.downloadFromInfo(info, {
      ...options,
      quality: "highestvideo"
    });
    // create the ffmpeg process for muxing
    let ffmpegProcess: any = cp.spawn(
      ffmpegPath.path,
      [
        // supress non-crucial messages
        "-loglevel",
        "8",
        "-hide_banner",
        // input audio and video by pipe
        "-i",
        "pipe:3",

        "-i",
        "pipe:4",
        // map audio and video correspondingly

        // no need to change the codec
        // output mp4 and pipe
        "-c:v",
        "libx264",
        "-x264opts",
        "fast_pskip=0:psy=0:deblock=-3,-3",
        "-preset",
        "veryslow",
        "-crf",
        "18",
        "-c",
        "copy",
        "-pix_fmt",
        "yuv420p",
        "-movflags",
        "frag_keyframe+empty_moov",
        "-g",
        "300",
        "-f",
        "mp4",

        "-map",
        "0:v",

        "-map",
        "1:a",

        "pipe:5"
      ],
      {
        // no popup window for Windows users
        windowsHide: true,
        stdio: [
          // silence stdin/out, forward stderr,
          "inherit",
          "inherit",
          "inherit",
          // and pipe audio, video, output
          "pipe",
          "pipe",
          "pipe"
        ]
      }
    );

    audioStream.pipe(ffmpegProcess.stdio[4]);
    videoStream.pipe(ffmpegProcess.stdio[3]);
    ffmpegProcess.stdio[5].pipe(result);
  });
  return result;
};


  


  I am playing around with tons of different arguments. The result of this video gets uploaded to a Google Bucket. Then when seeking in Chrome I am getting some issues with certain frames, they are not being seeked.

  


  When I pass it through FFMPEG locally and re-encode it, then upload it, I notice there are no issues.

  


  Here is an image comparing the two results when running ffmpeg -i FILE (the one on the left works fine and the differences are minor)

  


  

  


  I tried adjusting the arguments in the muxer code and am continuing to try and compare with the re-encoded video. I have no idea why this is happening, something to do with the frames.