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• Demuxing and decoding raw RTP with libavformat

  8 février 2023, par kevmo314

  I'm implementing a pipeline where I receive inbound RTP packets in memory but I'm having trouble figuring out how to set up libavformat to handle/unwrap the RTP packets.

  


  I have all relevant information about the underlying codec necessary but since it's h264 I cannot simply strip the RTP header trivially. I create the input context with goInputFunction writing one packet per invocation.

  


  void *readbuf = av_malloc(1500);
AVIOContext *avioreadctx = avio_alloc_context(readbuf, 1500, 0, transcoder, &goInputFunction, NULL, NULL);
AVFormatContext *inputctx = avformat_alloc_context();
inputctx->pb = avioreadctx;
inputctx->flags |= AVFMT_FLAG_CUSTOM_IO;


  


  When I open it with avformat_open_input(&inputctx, NULL, NULL, NULL) it repeatedly calls the read function but doesn't actually progress. I suspect because the RTP stream itself does not have enough information to fully describe the codec ? If I leave this open out, then av_read_frame(inputctx, input_packet) down the road segfaults, I'm guessing because the input context is uninitialized.

  


  So to my question, is it possible to set the codec details that the SDP would typically set, but manually ?

  


  I'm looking for an example of how to manually configure the AVFormatContext to consume RTP packets without an SDP and setting up a UDP port listener.

  


• Using hwaccel ffmpeg option with moviepy library

  12 octobre 2022, par Nicola Lepetit

  I am trying to add the hwaccel option of ffmpeg to a script I am working on in Python, based on the moviepy library, by passing the options via the ffmpeg_params parameter :

  


  from moviepy.editor import VideoFileClip

ASSETS_FOLDER = "./assets/backgrounds/road/"
video_file_name = "12386.mp4"
start_time = 5
end_time = 20
target_file = "output.mp4"

video = VideoFileClip(f"{ASSETS_FOLDER}{video_file_name}")
new = video.subclip(start_time, end_time)
new.fps = 25
new.write_videofile(target_file, ffmpeg_params= ['-hwaccel','cuda'])


  


  The problem is that these ffmpeg_params are added at the end of the ffmpeg command line, so I am getting the following error :

  


  [Errno 22] Invalid argument

MoviePy error: FFMPEG encountered the following error while writing file 
   ./assets/temp/3/cut1.mp4:

 b'Option hwaccel (use HW accelerated decoding) cannot be applied to output url 
  ./assets/temp/3/cut1.mp4 -- you are trying to apply an input option to an output file
  or vice versa. Move this option before the file it belongs to.\r\nError parsing
  options for output file ./assets/temp/3/cut1.mp4.\r\nError opening output files:
  Invalid argument\r\n'


  


  Is there another way to use the option with moviepy

  


• How to avoid ffmpeg failing to add chapters to mov file ?

  27 septembre 2022, par BabaG

  I've been trying all day to get ffmpeg to add chapters to a prores mov file. It does add the first two, but then it fails with the name of the text file and an error message :

  


  chapterstest_orig.txt: Invalid data found when processing input


  


  I see lots of online references to the format of both the ffmpeg command, as well as the text file containing the chapter metadata. Here are mine :

  


  ffmpeg -i chapterstest_orig.mov -i chapterstest_orig.txt -map_metadata 1 -codec copy chapterstest.mov


  


  i've also tried it with -map_chapters :

  


  ffmpeg -i chapterstest_orig.mov -i chapterstest_orig.txt -map_metadata 1 -map_chapters 1 -codec copy chapterstest.mov


  


  Here's a copy of my text file, containing the chapter info :

  


  ;FFMETADATA1
title=Angel's Gate Cultural Center
artist=Buzzworld

[CHAPTER]
TIMEBASE=1/1000
START=0
END=6999
title=Buzzworld 10-10-1997

[CHAPTER]
TIMEBASE=1/1000
START=7000
END=290999
title=The Road To Lisdoonvarna

[CHAPTER]
TIMEBASE=1/1000
START=291000
END=739999
title=Jack Orion

[CHAPTER]
TIMEBASE=1/1000
START=740000
END=992999
title=The Frieze Britches

[CHAPTER]
TIMEBASE=1/1000
START=993000
END=1295999
title=The Blackleg Miner

[CHAPTER]
TIMEBASE=1/1000
START=1296000
END=1559999
title=Johnny Jump Up

[CHAPTER]
TIMEBASE=1/1000
START=1560000
END=1867999
title=Tom Billy's

[CHAPTER]
TIMEBASE=1/1000
START=1868000
END=2143999
title=When Will We Be Married?

[CHAPTER]
TIMEBASE=1/1000
START=2144000
END=2500999
title=The Old Bush

[CHAPTER]
TIMEBASE=1/1000
START=2501000
END=2839000
title=Niamh's Capers


  


  If I delete everything after the second chapter, the file processes. It always fails if I add more chapters.

  


  I've also tried using things like :

  


  -map 0:v -map 0:a -map 0:s


  


  Any help is much appreciated. I'm kind of at my wits end here.

  


  Thanks.