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• Why does the PyAV-encoded video have a different total time in seconds than the original file

  13 octobre 2023, par Diego Medeiros

  I'm taking a mp4 file, decoding it frame by frame and reencoding it. I'm using PyAV and the reencoding is running on h265.
When the code is running, it seems that all frames are passed from the decoder to the encoder, but at the end I have a file with 3 seconds less. For longer videos I'll have bigger differences.

  


  I have already checked the fps, it comes out with a very small variation, even if I use the Fraction type to avoid decimal differences.

  


  I'd like to know if it's some parametrization error, or if this is something to do with the encoder itself like keyframes and all those sort of things. Is there a way to fix it ?

  


  import av


container = av.open('input.mp4')

# create an output container to receive the transcoded video packets
output_container = av.open('output.mp4', 'w', format='mp4')
# add a stream to output container with same fps as input and h265 codec
output_stream = output_container.add_stream(
    'libx265', rate=container.streams.video[0].average_rate)
# set the output stream size
output_stream.width = 640
output_stream.height = 480

print('Starting transcoding...')

actual_frame = 0
container_total_frames = container.streams.video[0].frames

# start decoding packets and reading frames from the container
try:
    for packet_input in container.demux():
        if packet_input.dts is None:
            break
        for frame in packet_input.decode():

            try:
                actual_frame += 1
                # convert the frame to a numpy array
                img = frame.to_ndarray(format='bgr24')

                # prepare the ndarray frame and encode it
                frame_nd = av.VideoFrame.from_ndarray(img, format='bgr24')
                packet_output = output_stream.encode(frame_nd)
                output_container.mux(packet_output)
                print('Frame: {}/{}'.format(actual_frame, container_total_frames))
            except Exception as e:
                print("Error writing frame: ", e)
                break
except Exception as e:
    print('Finished transcoding')

output_container.close()

print('Finished transcoding')



  


• ffmpeg makes video with no sound on video.js

  21 septembre 2023, par Laurent B

  I have this code that creates m3u8 file to stream a mkv file after transcoding.

  


  ffmpeg.setFfmpegPath(ffmpegPath);
childProcess = ffmpeg()
    .input(inputFilePath)
    // .native()
    .inputOptions(['-y', '-progress', 'pipe:1'])
    .outputOptions(['-b:v 1M', '-hls_time 2', '-hls_list_size 0', '-hls_segment_size 500000'])
    .output('public/output.m3u8')
    .on('end', () => {
        io.emit('conversionComplete', { percent: 100, time: totalDuration, totalDuration, timemark: millisecondsToTimeString(totalDuration) });
        childProcess = null
    })
    .on('error', (error) => {
        io.emit('conversionError', { error });
        childProcess = null
    })
    .on('progress', (progress) => {
        io.emit('conversionProgress', { ...progress, time: timeStringToMilliseconds(progress.timemark), totalDuration });
    });

childProcess.run();


  


  The m3u8 is readable by VLC Player and video.js and can be casted to Chrome Cast. For some others, 4Go files moreless, it works only when the video is transcoded without sound with option .inputOption('-an').

  


  Here's the content of m3u8

  


  #EXTM3U
#EXT-X-VERSION:3
#EXT-X-TARGETDURATION:10
#EXT-X-MEDIA-SEQUENCE:4
#EXTINF:10.000000,
output4.ts
#EXTINF:10.000000,
output5.ts
#EXTINF:8.640000,
output6.ts
#EXTINF:10.000000,
output7.ts
#EXTINF:10.000000,
output8.ts


  


  

  • I tried with all possible audio codecs provided by ffmpeg

  


  • I tried with bigger/smaller parts for ts files

  


  • I tried with other bitrate

  


  


  Thanks in advance for your ideas

  


• ffmpeg scale question.It succeed when the size is 2048,but when 4096 failed [closed]

  7 septembre 2023, par 徐谷歌

  if :

  


  ffmpeg -y -loop 1 -i ./rebirth/image4.png -loop 1 -t 1.4 -i temp.png -filter_complex "[0]scale=2048:2048[video0],[video0][1]xfade=transition=fade:duration=0.8:offset=0.1" -c:v libx264 -r 30 -pix_fmt yuv444p temp.mp4


  


  it goes right.but when temp.png is bigger,it goes wrong,like :

  


  ffmpeg -y -loop 1 -i ./rebirth/image4.png -loop 1 -t 1.4 -i temp.png -filter_complex "[0]scale=4096:4096[video0],[video0][1]xfade=transition=fade:duration=0.8:offset=0.1" -c:v libx264 -r 30 -pix_fmt yuv444p temp.mp4


  


  I have enlarge the temp.png in the 2nd example.the size of image4.png is 1152x1152.