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• FFmpeg possible bug with -pre flag

  5 juin 2021, par Slav

  I was studying the ffpresets and avpresets but I stumbled upon something interesting.

  


  According to the ffmpeg docs :

  


  


  First ffmpeg searches for a file named codec_name-arg.avpreset in the above-mentioned directories, where codec_name is the name of the codec to which the preset file options will be applied. For example, if you select the video codec with -vcodec libvpx and use -pre 1080p, then it will search for the file libvpx-1080p.avpreset.

  


  


  


  If no such file is found, then ffmpeg will search for a file named arg.avpreset in the same directories.

  


  


  I have a preset stored in the correct directory :

  


  $ ls ~/.avconv/
libvpx-1080p.avpreset


  


  Therefore, the following command should work :

  


  $ ffmpeg -i input.mp4 -vcodec libvpx -pre 1080p output.mp4 


  


  But instead it results in the follwing error :

  


  Preset 1080p specified for stream 0:1, but could not be opened.


  


  However, the following command works :

  


  ffmpeg -i input.mp4 -vcodec libvpx -pre libvpx-1080p output.mp4


  


  Is this a bug or am I misunderstanding the docs ?

  


  EDIT : I originally tried with the latest ffmpeg version available from the repositories (4.3.1). However, I then decided to confirm this is still the case with the latest version built from source, which yields :

  


  ~/Downloads/FFmpeg$ ./ffmpeg --version
ffmpeg version N-102649-g3ac7d99428 Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 10 (Ubuntu 10.2.0-13ubuntu1)
configuration: --disable-x86asm --enable-libvpx
libavutil      57.  0.100 / 57.  0.100
libavcodec     59.  1.100 / 59.  1.100
libavformat    59.  2.101 / 59.  2.101
libavdevice    59.  0.100 / 59.  0.100
libavfilter     8.  0.101 /  8.  0.101
libswscale      6.  0.100 /  6.  0.100
libswresample   4.  0.100 /  4.  0.100


  


  EDIT 2 : Adding the whole log of the failing command as requested

  


  $ ./ffmpeg -i ../input.mp4 -vcodec libvpx -pre 1080p ../output.mp4
ffmpeg version N-102649-g3ac7d99428 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10 (Ubuntu 10.2.0-13ubuntu1)
  configuration: --disable-x86asm --enable-libvpx
  libavutil      57.  0.100 / 57.  0.100
  libavcodec     59.  1.100 / 59.  1.100
  libavformat    59.  2.101 / 59.  2.101
  libavdevice    59.  0.100 / 59.  0.100
  libavfilter     8.  0.101 /  8.  0.101
  libswscale      6.  0.100 /  6.  0.100
  libswresample   4.  0.100 /  4.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '../input.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: mp42mp41isomavc1
    creation_time   : 2015-08-07T09:13:36.000000Z
  Duration: 00:00:30.53, start: 0.000000, bitrate: 4675 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 4486 kb/s, 30 fps, 30 tbr, 30 tbn (default)
    Metadata:
      creation_time   : 2015-08-07T09:13:36.000000Z
      handler_name    : L-SMASH Video Handler
      vendor_id       : [0][0][0][0]
      encoder         : AVC Coding
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 256 kb/s (default)
    Metadata:
      creation_time   : 2015-08-07T09:13:36.000000Z
      handler_name    : L-SMASH Audio Handler
      vendor_id       : [0][0][0][0]
Preset 1080p specified for stream 0:1, but could not be opened.


  


• Gstreamer preserve timestamp when encoding ts segments

  1er juillet 2021, par Guru Govindan

  I have a series of ts files(h265) which are part of a m3u8 manifest which are fed into the pipeline through fdsrc. I use the following pipeline to transcode them to H264 to be played on a Hlsjs web browser.

  


  cat 2021-06-30T00-55-41Z_2000000.ts | gst-launch-1.0  -q mpegtsmux name=mux ! fdsink fd=1 fdsrc ! tsdemux name=demux demux. ! queue ! h265parse ! nvh265dec ! videoconvert ! videoscale ! video/x-raw,width=640,height=360 ! nvh264enc ! mux.


  


  The individual ts segments are transcoded successfully and can be played.

  


  However the DTS is out of aligment and when these ts segments are played as part of the hls manifest, it is not able to play as DTS is out of order.

  


  [mpegts @ 0x7fb69100a400] DTS 6496420096 < 6496446847 out of order
[hls @ 0x7fb69580ea00] DTS 6496420096 < 6496446847 out of order


  


  In FFMPEG we have copyts to preserve the timestamp.
Is there something similar in gstreamer to preserve the timestamp ? Or atleast generate a timestamp with the current time so that the player doesnt complain ?

  


  I tried fdsrc do-timestamp=true but that didnt work.

  


  I appreciate any help in this.

  


  Best

  


• operations (resize, crop...) over images with output pipeline using ffmpeg

  7 juin 2021, par Ondřej Dobrovolný

  I have been experimenting with ffmpeg in C# using System.Diagnostics.Process. Im trying to do some basic operations such as resizing, croping and adding watermarks over image. So far i managed everything well but now i am trying to load image from some storage (C :/ ....), do some operation and then use pipeline to feed the image to memory so that i can work with it further.
This is the command itself

  


  "-i C:\Work\PrivateTestingRepos\ImageProcessingTest\MyTestingApplication\FfmpegProcessTest\src\guid.jpg -vf "scale=1024:768" -f png_pipe pipe:1"


  


  and this produces following error :

  


  error: ffmpeg version N-102608-g7a879cce37 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10-win32 (GCC) 20210408
  configuration: --prefix=/ffbuild/prefix --pkg-config-flags=--static --pkg-config=pkg-config --cross-prefix=x86_64-w64-mingw32- --arch=x86_64 --target-os=mingw32 --enable-gpl --enable-version3 --disable-debug --disable-w32thread
s --enable-pthreads --enable-iconv --enable-libxml2 --enable-zlib --enable-libfreetype --enable-libfribidi --enable-gmp --enable-lzma --enable-fontconfig --enable-libvorbis --enable-opencl --enable-libvmaf --enable-vulkan --enabl
e-amf --enable-libaom --enable-avisynth --enable-libdav1d --enable-libdavs2 --enable-ffnvcodec --enable-cuda-llvm --enable-libglslang --enable-libgme --enable-libass --enable-libbluray --enable-libmp3lame --enable-libopus --enabl
e-libtheora --enable-libvpx --enable-libwebp --enable-lv2 --enable-libmfx --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librav1e --enable-librubberband --enable-schannel --enable-sdl2 --enabl
e-libsoxr --enable-libsrt --enable-libsvtav1 --enable-libtwolame --enable-libuavs3d --enable-libvidstab --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libzimg --extra-cflags=-DLIBTWOLAME_STATIC --ex
tra-cxxflags= --extra-ldflags=-pthread --extra-ldexeflags= --extra-libs=-lgomp
  libavutil      57.  0.100 / 57.  0.100
  libavcodec     59.  1.100 / 59.  1.100
  libavformat    59.  2.101 / 59.  2.101
  libavdevice    59.  0.100 / 59.  0.100
  libavfilter     8.  0.101 /  8.  0.101
  libswscale      6.  0.100 /  6.  0.100
  libswresample   4.  0.100 /  4.  0.100
  libpostproc    56.  0.100 / 56.  0.100
Input #0, image2, from 'C:\Work\PrivateTestingRepos\ImageProcessingTest\MyTestingApplication\FfmpegProcessTest\src\guid.jpg':
  Duration: 00:00:00.04, start: 0.000000, bitrate: 280300 kb/s
  Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 2735x1904, 25 fps, 25 tbr, 25 tbn
[NULL @ 0000024cfa5d8400] Requested output format 'png_pipe' is not a suitable output format
pipe:1: Invalid argument


  


  From error it look like ffmpeg tries to load the image as Image2 which is some kind of video format and when i tell it to save it as png pipeline it throws error which is understandable.
Is there some way of using ffmpeg to this kind of operations over images ? Iam aware that its mostly used for videos and images are secondary feature.
If necessary i can provide source codes.
Thanks for your time ! :)