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• Create thumbnails from a timestamp list with ffmpeg [on hold]

  10 septembre 2015, par dvdmn

  I need to create 100+ thumbnails from a big video file (>4gb) and thumbnail points in video will be random (another app will create a time list during recording)

  Is there a special parameter to create all the thumbnails within 1 command with a list file ? (Something similar to stitching video files).

  ie : ffmpeg -thumbnail -i times.txt...

  PS : it does not have to be ffmpeg, I am open to alternative solutions

• Desktop audio falls behind when recording microphone + desktop audio + screen using ffmpeg

  15 septembre 2013, par madr

  I have put together this script for recording the microphone, the desktop audio and the screen using ffmpeg :

  DATE=`which date`
  
  RESO=2560x1440
  
  FPS=30
  
  PRESET=ultrafast
  
  DIRECTORY=$HOME/Video/
  
  FILENAME=videocast`$DATE +%d%m%Y_%H.%M.%S`.mkv
  
  
  
  ffmpeg -y -vsync 1 \
  
  -f pulse -ac 2 -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor \
  
  -f pulse -ac 1 -ar 25000 -i alsa_input.usb-0d8c_C-Media_USB_Headphone_Set-00-Set.analog-mono \
  
  -filter_complex aresample=async=1,amix=duration=shortest,apad \
  
  -f x11grab -r $FPS -s $RESO -i :0.0 \
  
  -acodec libvorbis \
  
  -vcodec libx264 -pix_fmt yuv420p -preset $PRESET -threads 0 \
  
  $DIRECTORY$FILENAME

  Everything is recorded and between the screen and the microphone sound there are no issues what so ever, however the desktop audio falls behind badly.

  It begins in sync but gets worse over time during playback, also in ffplay. It does not matter what application playing sound : both Youtube-videos in the browser, desktop sounds and Rhythmbox (playing a couple of seconds of song then stops, wait and repeat) gets out of sync.

  The terminal output complain about

  "ALSA lib pcm.c:7843:(snd_pcm_recover) overrun occurred22.73 bitrate=10384.5kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred" 

  and similar but I do not know what that means.

  Full terminal output here :

  ffmpeg version 2.0.1 Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Aug 11 2013 14:52:28 with gcc 4.8.1 (GCC) 20130725 (prerelease)
  
    configuration: --prefix=/usr --disable-debug --disable-static --enable-avresample --enable-dxva2 --enable-fontconfig --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --enable-pic --enable-postproc --enable-runtime-cpudetect --enable-shared --enable-swresample --enable-vdpau --enable-version3 --enable-x11grab
  
    libavutil      52. 38.100 / 52. 38.100
  
    libavcodec     55. 18.102 / 55. 18.102
  
    libavformat    55. 12.100 / 55. 12.100
  
    libavdevice    55.  3.100 / 55.  3.100
  
    libavfilter     3. 79.101 /  3. 79.101
  
    libavresample   1.  1.  0 /  1.  1.  0
  
    libswscale      2.  3.100 /  2.  3.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  3.100 / 52.  3.100
  
  Guessed Channel Layout for  Input Stream #0.0 : stereo
  
  Input #0, pulse, from 'alsa_output.pci-0000_00_1b.0.analog-stereo.monitor':
  
    Duration: N/A, start: 0.014093, bitrate: 1536 kb/s
  
      Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
  
  Guessed Channel Layout for  Input Stream #1.0 : mono
  
  Input #1, pulse, from 'alsa_input.usb-0d8c_C-Media_USB_Headphone_Set-00-Set.analog-mono':
  
    Duration: N/A, start: 0.006172, bitrate: 400 kb/s
  
      Stream #1:0: Audio: pcm_s16le, 25000 Hz, mono, s16, 400 kb/s
  
  [x11grab @ 0x218a6e0] device: :0.0 -> display: :0.0 x: 0 y: 0 width: 2560 height: 1440
  
  [x11grab @ 0x218a6e0] shared memory extension found
  
  Input #2, x11grab, from ':0.0':
  
    Duration: N/A, start: 1379021580.184321, bitrate: N/A
  
      Stream #2:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 2560x1440, -2147483 kb/s, 30 tbr, 1000k tbn, 30 tbc
  
  [libx264 @ 0x21ae560] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
  
  [libx264 @ 0x21ae560] profile Constrained Baseline, level 5.0
  
  [libx264 @ 0x21ae560] 264 - core 133 r2339 585324f - H.264/MPEG-4 AVC codec - Copyleft 2003-2013 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
  
  Output #0, matroska, to '/home/anders/Video/videocast12092013_23.33.00.mkv':
  
    Metadata:
  
      encoder         : Lavf55.12.100
  
      Stream #0:0: Audio: vorbis (libvorbis) (oV[0][0] / 0x566F), 25000 Hz, mono, fltp
  
      Stream #0:1: Video: h264 (libx264) (H264 / 0x34363248), yuv420p, 2560x1440, q=-1--1, 1k tbn, 30 tbc
  
  Stream mapping:
  
    Stream #0:0 (pcm_s16le) -> aresample (graph 0)
  
    Stream #1:0 (pcm_s16le) -> amix:input1 (graph 0)
  
    amix (graph 0) -> Stream #0:0 (libvorbis)
  
    Stream #2:0 -> #0:1 (rawvideo -> libx264)
  
  Press [q] to stop, [?] for help
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) overrun occurred22.73 bitrate=10384.5kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred3.22 bitrate=10423.3kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) overrun occurred25.25 bitrate=11011.0kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred5.76 bitrate=11013.7kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) overrun occurred27.25 bitrate=11175.4kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred7.76 bitrate=11168.7kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred8.24 bitrate=11176.4kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) overrun occurred55.48 bitrate=11243.8kbits/s    
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred
  
  ALSA lib pcm.c:7843:(snd_pcm_recover) underrun occurred
  
  frame=12871 fps= 30 q=-1.0 Lsize=  542369kB time=00:07:09.31 bitrate=10349.3kbits/s    
  
  video:539762kB audio:2363kB subtitle:0 global headers:3kB muxing overhead 0.044476%
  
  [libx264 @ 0x21ae560] frame I:52    Avg QP:15.46  size:725888
  
  [libx264 @ 0x21ae560] frame P:12819 Avg QP:18.26  size: 40172
  
  [libx264 @ 0x21ae560] mb I  I16..4: 100.0%  0.0%  0.0%
  
  [libx264 @ 0x21ae560] mb P  I16..4:  2.6%  0.0%  0.0%  P16..4: 18.1%  0.0%  0.0%  0.0%  0.0%    skip:79.3%
  
  [libx264 @ 0x21ae560] coded y,uvDC,uvAC intra: 57.8% 49.8% 25.3% inter: 8.9% 8.7% 2.2%
  
  [libx264 @ 0x21ae560] i16 v,h,dc,p: 23% 29% 32% 16%
  
  [libx264 @ 0x21ae560] i8c dc,h,v,p: 45% 28% 18%  9%
  
  [libx264 @ 0x21ae560] kb/s:10306.26

  Please help me, I am really close to get this working !

  UPDATE : The desktop audio is out of sync when skipping filter_complex and microphone also, bit in a smaller amount. Using copy instead of libvorbis does not change anything either.

• equivalent option in ffmpeg for ffplay's -infbuff

  25 septembre 2015, par Paul

  I have a multicast UDP stream that I can watch (with almost no errors) if I use ffplay’s infbuf option.

  But when I try to encode it via ffmpeg, ffmpeg reports a lot of errors and the resultant video has lots of errors.

  I have tried setting the fifo_size to a super large value like 655360 and the buf_size as per https://www.ffmpeg.org/ffmpeg-protocols.html#udp. But none of gets rid of the decode errors in ffmpeg.

  Is it possible to provide settings to ffmpeg that do something similar to what ffplay’s -intbuf does ? I want my video encode to be as error free as video playback via ffplay.