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• indeo4 : expand allowed quantiser range

  31 mai 2013, par Kostya Shishkov

  indeo4 : expand allowed quantiser range
  Indeo 4 has quantiser range 0-31 instead of 0-23 for Indeo 5, and clipping
  
  quantiser leads to incorrect quantisation and DC prediction on low-quality
  
  videos.
  This fixes bug 259.
  

  • [DBH] libavcodec/ivi_common.c

• ffmpeg demux concat video output blinks/stuttering between joined clips

  11 juin 2024, par hieroshima

  I'm experiencing a strange issue with FFmpeg after partially joining a few MP4 clips into one output file (output.mp4). The problem is that the video between clips randomly blinks or stutters, showing frames from the previous scene in the next scene. This happens in a completely random manner.

  


  All my MP4 clips have the same FPS, TBR, and TBN values, except for the bitrate (bolded below), which varies for each clip. These clips were prepared and encoded using AWS MediaConvert to ensure they have consistent parameters.

  


  Here’s the ffprobe result for one of the clips :

  


  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661),
yuv420p(progressive), 640x360 [SAR 1:1 DAR 16:9], **84 kb/s**, 29.97 fps,
29.97 tbr, 30k tbn (default)


  


  Below is my input.txt file for concatenation :

  


  file 'clip1_360.mp4' 
outpoint 00:00:04.00
file 'clip2_360.mp4' 
outpoint 00:00:03.00
file 'clip3_360.mp4' 
outpoint 00:00:04.00


  


  The FFmpeg command I'm using to concatenate the clips is :

  


  ffmpeg -y -f concat -safe 0 -protocol_whitelist
file,http,https,tcp,tls -fflags +igndts -i input.txt -c copy output/output.mp4


  


  I use the -fflags +igndts flag because I receive warnings about non-monotonic DTS. I’m employing the concat demuxer to avoid re-encoding the video, as the time required to generate the output is crucial. This is why I have prepared and encoded all clips in advance to have consistent values.

  


  Here is screen recording from my video player to see this problem :

  


  https://youtu.be/SfWnCbMeOfw

  


  Any assistance or suggestions on how to resolve this issue would be greatly appreciated. Because I don't have any more idea what I can do with this. If you need some more details which I didn't provide, please let me know.

  


• FFMPEG - how to identify a bottleneck in hardware transcoding ?

  26 août 2021, par Henry

  In the provided example I was trying to transcode a 4K h264 source to a 1080p h264 output using Nvidia's Hardware acceleration.

  


  Relevant information :

  


  ffmpeg version git-2017-12-25-613f789 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.2.0 (GCC)
  configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-bzlib --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-amf --enable-cuda --enable-cuvid --enable-d3d11va --enable-nvenc --enable-dxva2 --enable-avisynth --enable-libmfx
  libavutil      56.  7.100 / 56.  7.100
  libavcodec     58.  9.100 / 58.  9.100
  libavformat    58.  3.100 / 58.  3.100
  libavdevice    58.  0.100 / 58.  0.100
  libavfilter     7.  7.100 /  7.  7.100
  libswscale      5.  0.101 /  5.  0.101
  libswresample   3.  0.101 /  3.  0.101
  libpostproc    55.  0.100 / 55.  0.100


  


  Command used :

  


  ffmpeg -c:v h264_cuvid -i "4K_input.mp4" -c:v h264_nvenc -preset slow -s 1920x1080 -c:a copy output.mkv


  


  Relevant PC Specs :

  


  GPU: (Gigabyte) GeForce GTX 1070 Ti
CPU: Intel Core i7 7700K
Memory: 8GB DDR4 2400MHz Single Channel.
SSD: Crucial CT525MX3


  


  While the Nvidia Desktop recording has absolutely no issues to record live h264 video in up to 50Mbps bitrates, this encoding at below 2600kbps was extremely slow utilizing barely 35% GPU.
I was unable to utilize 100% of the GPU on any video parameters.

  


  This is why I could use some advice concerning how to identify a (suspected) bottleneck.