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• How to extract motion vectors from h264 without a full decode on the CPU

  25 septembre 2020, par Adrian May

  I'm trying to use my nose as a pointing device. The plan is to encode the video stream from a webcam pointed at my face as h264 or the like, get the motion vectors, cook the numbers a bit and chuck them into /dev/uinput to make the mouse pointer move about. The uinput bit was easy.

  


  This has to work with zero discernable latency. This, for instance :

  


  #!/bin/bash
[ -p pipe.mkv ] || mkfifo pipe.mkv
ffmpeg -y -rtbufsize 1M -s 640x360 -vcodec mjpeg -i /dev/video0 -c h264_nvenc pipe.mkv &
ffplay -flags2 +export_mvs -vf codecview=mv=pf+bf+bb pipe.mkv


  


  shows that the vectors are there but with a latency of several seconds which is unusable in a mouse. I know that the first ffmpeg step is working very fast by using the GPU, so either the pipe or the h264 decode in the second step is introducing the latency.

  


  I tried MV Tractus (same as mpegflow I think) in a similar pipe arrangement and it was also very slow. They do a full h264 decode on the CPU and I think that's the problem cos I can see them imposing a lot of load on one CPU. If the pipe had caused the delay by buffering badly then the CPU wouldn't have been loaded. I guess ffplay also did the decoding on the CPU and I couldn't persuade it not to, but it only wants to draw arrows which are no use to me.

  


  I think there are several approaches, and I'd like advice on which would be best, or if there's something even better I don't know about. I could :

  


  

  • Decode in hardware and get the motion vectors. So far this has failed. I tried combining ffmpeg's extract_mvs.c and hw_decode.c samples but no motion vectors turn up. vdpau is the only decoder I got working on my linux box. I have a nvidia gpu.

  


  • Do a minimal parse of the h264 to fish out the motion vectors only, ignoring all the other data. I think this would mean putting some kind of "motion only" option in libav's parser, but I'm not at all familiar with that code.

  


  • Find some other h264 parsing library that has said option and also unpacks the container.

  


  • Forget about hardware accelerated encoding and use a stripped down encoder to make only the motion vectors on either CPU or GPU. I suspect this would be slow cos I think calculating the motion vectors is the hardest part of the algorithm.

  


  


  I'm tending towards the second option but I need some help figuring out where in the libav code to do it.

  


• How to use FFmpeg and GeForce Hardware to decode and encode 4K MKV movie to 1080p [closed]

  27 janvier 2023, par slyfox1186

  I am struggling with the instruction provided to convert a 4k Movie to 1080p so I can run it easier on my plex server.

  


  I have a Geforce 1080Ti and have enable cuda and all the necessary options when building ffmpeg.

  


  I keep getting a weird error and I am stuck at the below point.

  


  Here is my code that I am working on currently

  


  REM @ECHO OFF
SETLOCAL ENABLEDELAYEDEXPANSION
COLOR 0A
TITLE CONVERT 4K TO 1080P USING GEFORCE HW

PUSHD "%~dp0"

SET "FF=C:\MAB\local64\bin-video\ffmpeg.exe"

FOR /R %%G IN (*.mkv) DO (
    "%FF%" -hide_banner -hwaccel cuda -y -i "%%~dpnG.mkv" -c:v h264_nvenc -preset slow -pix_fmts yuv420p10le -vf scale='1920:-1' -c:a copy "%%~dpnG(1080p).mkv"
    )

ECHO.
PAUSE
EXIT



  


  below is the error output I get when running the above command

  


  Guessed Channel Layout for Input Stream #0.1 : 5.1
Input #0, matroska,webm, from 'Mulan_2020.mkv':
  Metadata:
    title           : mandtv.net
    encoder         : libebml v1.4.0 + libmatroska v1.6.2
    creation_time   : 2020-09-10T05:08:02.000000Z
  Duration: 01:55:08.70, start: 0.000000, bitrate: 16704 kb/s
    Stream #0:0(eng): Video: hevc (Main 10), yuv420p10le(tv, bt2020nc/bt2020/smpte2084), 3840x1608 [SAR 1:1 DAR 160:67], 23.98 fps, 23.98 tbr, 1k tbn, 23.98 tbc (default)
    Metadata:
      BPS-eng         : 15933746
      DURATION-eng    : 01:55:08.652000000
      NUMBER_OF_FRAMES-eng: 165642
      NUMBER_OF_BYTES-eng: 13760089087
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:1(eng): Audio: eac3, 48000 Hz, 5.1, fltp (default) (forced)
    Metadata:
      title           : En
      BPS-eng         : 768000
      DURATION-eng    : 01:55:08.704000000
      NUMBER_OF_FRAMES-eng: 215897
      NUMBER_OF_BYTES-eng: 663235584
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:2(eng): Subtitle: subrip
    Metadata:
      title           : English
      BPS-eng         : 35
      DURATION-eng    : 01:50:28.504000000
      NUMBER_OF_FRAMES-eng: 1150
      NUMBER_OF_BYTES-eng: 29135
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:3(ger): Subtitle: subrip
    Metadata:
      title           : de
      BPS-eng         : 2
      DURATION-eng    : 00:03:07.062000000
      NUMBER_OF_FRAMES-eng: 2
      NUMBER_OF_BYTES-eng: 53
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:4(ger): Subtitle: subrip
    Metadata:
      title           : de
      BPS-eng         : 27
      DURATION-eng    : 01:54:16.482000000
      NUMBER_OF_FRAMES-eng: 933
      NUMBER_OF_BYTES-eng: 23256
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:5(fre): Subtitle: subrip
    Metadata:
      title           : fr
      BPS-eng         : 0
      DURATION-eng    : 01:40:51.510000000
      NUMBER_OF_FRAMES-eng: 21
      NUMBER_OF_BYTES-eng: 380
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:6(fre): Subtitle: subrip
    Metadata:
      title           : fr
      BPS-eng         : 29
      DURATION-eng    : 01:54:19.902000000
      NUMBER_OF_FRAMES-eng: 806
      NUMBER_OF_BYTES-eng: 25098
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:7(spa): Subtitle: subrip
    Metadata:
      title           : es
      BPS-eng         : 2
      DURATION-eng    : 00:03:21.201000000
      NUMBER_OF_FRAMES-eng: 3
      NUMBER_OF_BYTES-eng: 73
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:8(spa): Subtitle: subrip
    Metadata:
      title           : es
      BPS-eng         : 30
      DURATION-eng    : 01:43:53.693000000
      NUMBER_OF_FRAMES-eng: 783
      NUMBER_OF_BYTES-eng: 24134
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:9(ita): Subtitle: subrip
    Metadata:
      title           : it
      BPS-eng         : 2
      DURATION-eng    : 00:03:08.522000000
      NUMBER_OF_FRAMES-eng: 2
      NUMBER_OF_BYTES-eng: 67
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:10(ita): Subtitle: subrip
    Metadata:
      title           : it
      BPS-eng         : 27
      DURATION-eng    : 01:54:16.649000000
      NUMBER_OF_FRAMES-eng: 784
      NUMBER_OF_BYTES-eng: 23506
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:11(por): Subtitle: subrip
    Metadata:
      title           : pt
      BPS-eng         : 27
      DURATION-eng    : 01:54:16.649000000
      NUMBER_OF_FRAMES-eng: 784
      NUMBER_OF_BYTES-eng: 23202
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:12(por): Subtitle: subrip
    Metadata:
      title           : pt
      BPS-eng         : 2
      DURATION-eng    : 00:03:08.522000000
      NUMBER_OF_FRAMES-eng: 2
      NUMBER_OF_BYTES-eng: 61
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:13(rus): Subtitle: subrip (default)
    Metadata:
      title           : ru
      BPS-eng         : 0
      DURATION-eng    : 01:37:43.480000000
      NUMBER_OF_FRAMES-eng: 9
      NUMBER_OF_BYTES-eng: 420
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:14(rus): Subtitle: subrip
    Metadata:
      title           : ru
      BPS-eng         : 50
      DURATION-eng    : 01:44:17.000000000
      NUMBER_OF_FRAMES-eng: 850
      NUMBER_OF_BYTES-eng: 39721
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
    Stream #0:15(ukr): Subtitle: subrip
    Metadata:
      title           : uk
      BPS-eng         : 50
      DURATION-eng    : 01:43:53.650000000
      NUMBER_OF_FRAMES-eng: 848
      NUMBER_OF_BYTES-eng: 39165
      _STATISTICS_WRITING_APP-eng: mkvmerge v50.0.0 ('Awakenings') 64-bit
      _STATISTICS_WRITING_DATE_UTC-eng: 2020-09-10 05:08:02
      _STATISTICS_TAGS-eng: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
Stream mapping:
  Stream #0:0 -> #0:0 (hevc (native) -> h264 (h264_nvenc))
  Stream #0:1 -> #0:1 (copy)
  Stream #0:2 -> #0:2 (subrip (srt) -> ass (ssa))
Press [q] to stop, [?] for help
[h264_nvenc @ 000002306685ccc0] 10 bit encode not supported
[h264_nvenc @ 000002306685ccc0] Provided device doesn't support required NVENC features
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!


  


  Can anyone spot what I'm missing ?

  


• FFmpeg tile crop paging when full

  19 janvier 2021, par Jimmy

  I've been trying to tile images from a video into a 10x10 image,it works but when the image is filled 10x10 it won't create another image and fill, it just stopped,

  


  This is what I ended up with :
ffmpeg -i video.mp4 -frames 1 -vf "select=not(mod(n,10)),scale=80:45,tile=10x10" out%03d.png

  


  What I wanted :

  


  

  • a tile with 10x10

  


  • when the image is filled, create another image and fill and so on, the outcome will be out1.png, out2.png... until it's done