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• Transcode from a live m3u8 using -ss

  20 août 2015, par pgm

  I’m trying to create a VOD hls clip from a live hls stream on adobe media server using ffmpeg and nodejs.

  An example of the command I’m using looks like this :

  ffmpeg -report -analyzeduration 999999999 -probesize 999999999 -ss 50 -i http://live.m3u8 -y -r 29.97 -threads 0 -hls_list_size 0 -c:v copy -a:v copy streamoutput.m3u8

  The problem is the -ss param (start time) is calculating the start time from the live point on the stream, rather than from the first ’ts’ fragment. I’d like to be able to encode inside of a "DVR window," meaning seeking from the beginning of the stream, not from the live point of the stream.

  Example : I use the param -ss 50 and it won’t encode for 50 seconds until the live stream catches up, outputting this in the ffmpeg log :

  [h264 @ 0000000002beae00] non-existing PPS 0 referenced
  
  [h264 @ 0000000002beae00] non-existing PPS 0 referenced
  
  [h264 @ 0000000002beae00] decode_slice_header error

  Once the live stream catches up to the 50 second delay it begins encoding. It works this way when I use -ss as either an input parameter or output parameter.

  Is there a way to accomplish this ? I’ve noticed that if I leave -ss completely out of the command, it will start at the beginning of the stream, but as soon as it’s there, even as a 0, it will start at the "live point."

  Any help is much appreciated !

• Getting an error from pyffmpeg when running as a submodule

  3 décembre 2023, par Devin Gardner

  I'm working on building an API using pyffmpeg and pytube to download YouTube videos and convert them to .wav files, synced up with some LED animations. I'm importing pyffmpeg in a submodule, which is then imported by yet another submodule. I'm getting the following error when I run the script (both from my entire package, and in the Python shell directly, and on two different devices with two different OSes) :

  


  This is the error I get from the shell on my MacBook :

  


  Traceback (most recent call last):&#xA;  File "<stdin>", line 1, in <module>&#xA;  File "/path/to/venv/lib/python3.11/site-packages/pyffmpeg/__init__.py", line 163, in convert&#xA;    raise Exception(self.error)&#xA;Exception&#xA;</module></stdin>

  


  And this is the error I get on my Raspberry Pi when I run the full program :

  


    File "/path/to/venv/lib/python3.11/site-packages/pyffmpeg/__init__.py", line 154, in convert
    if 'Output #0' not in stderr:
                          ^^^^^^
UnboundLocalError: cannot access local variable 'stderr' where it is not associated with a value


  


  I've tracked down the relevant code in the __init__.py file of pyffmpeg, but I'm not sure how to fix the problem.

  


          if 'Output #0' not in stderr:
            lines = stderr.splitlines()
            if len(lines) > 0:
                self.error = lines[-1]
            else:
                self.error = ""

            if self.enable_log:
                self.logger.error(self.error)
            raise Exception(self.error)
        else:
            self.error = ''
            if self.enable_log:
                self.logger.info('Conversion Done')
        return out


  


  Anyone have any ideas ?

  


• Making colour of MP4 video consistent in Chrome

  21 septembre 2021, par OneWorld

  I see a difference in the colour of a video between different machines using different browsers. I was wondering what the cause of the difference is ?

  


  I use FFMPEG to create the video. I sent the video to three different people with slightly different machines, and slightly different Chrome versions, to try and see where the differences are.

  


  The FFMPEG output from the video is as follows :-

  


  ffmpeg version 3.2.2-static http://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.4.1 (Debian 5.4.1-4) 20161202
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-5 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gray --enable-libass --enable-libfreetype --enable-libfribidi --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libzimg
  libavutil      55. 34.100 / 55. 34.100
  libavcodec     57. 64.101 / 57. 64.101
  libavformat    57. 56.100 / 57. 56.100
  libavdevice    57.  1.100 / 57.  1.100
  libavfilter     6. 65.100 /  6. 65.100
  libswscale      4.  2.100 /  4.  2.100
  libswresample   2.  3.100 /  2.  3.100
  libpostproc    54.  1.100 / 54.  1.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'red_and_yellow_uat.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf57.56.100
  Duration: 00:00:03.00, start: 0.000000, bitrate: 84 kb/s
    Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p(tv, unknown/bt709/bt709), 1080x1080, 81 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler


  


  From the same UAT rendered Video, with screenshots taken in Chrome from person 1, person 2, person 3, and person 4, and using GIMP colour picker on my machine from the screenshots, the results for red, and yellow are as follows.

  


  Person 1:- #A83833  and  #FFCB2E  Chrome Version 92.0.4515.131 (Official Build) (64-bit)
Person 2:- #AB3334  and  #FFCA38  Chrome Version 92.0.4515.107


  


  (Note : these colours Match / are very close to the original).

  


  Both these machines above are 64 bit Ubuntu machines, using Ubuntu 18.04.5 LTS
We both use the gnome screenshot tool in Ubuntu to take the screenshot, which creates an 8bit PNG.

  


  Person 3:-    #B14039  and  #FED303  Chrome Version 93.0.4577.63 (Official Build) (x86_64)
Person 4:-    #B2403A  and  #FFD201  Chrome Version 92.0.4515.159 (Official Build) (x86_64)


  


  Mac screenshots are taken using cmd shift 4, and generate an 8bit PNG file.

  


  Person 3 Machine Spec :-
Machine :- Macbook Pro (2019)
OS : macOS Big Sur Version 11.5.2
Processor :- 2.6Ghz Intel Core i7 processor. 32bit architecture (typing arch in her tty terminal returns i386).
Graphics :- Intel UHD Graphics 630 1536

  


  Person 4 Machine Spec :-
Machine :- Macbook Pro (Retina, 2015)
OS :- MacOS Mojave, Version 10.14.6
Processor :- 2.5GHz, Intel Core i7
Graphics :- AMD Radeon R9, M370X 2 GB Intel Iris Pro 1536 MB

  


  Person 1 screenshot

  


  

  


  Person 2 screenshot

  


  

  


  Person 3 screenshot

  


  

  


  Person 4 screenshot

  


  

  


  Any suggestions anyone has to make these colours consistent would be much appreciated. Would love to know why it happens also ? If anyone can explain ?