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• Are their technical reasons is MP4 more popular than Webm ?

  1er juin 2019, par dprogramz

  Not looking for opinions. I’m searching for data.

  As it is now, I want to become a webM evangelist. However, I assume there are some actual technical reasons why mp4 is preferred over webm in the bigger picture. I want to know them so I can be accurate in my assessments.

  I’m working on developing a broadcast video messaging graphics engine (think chyron) and using the Chromium engine like OBS does for messaging. So far the results have been excellent.

  One of the best features I’ve found is using webm for video. I should note I am using small (640x480 max) videos as graphics that are on top off a larger full HD video.

  Not only does it seem to have a better compresion:quality ratio than mp4 for my use case, the most important thing is that it has full alpha support, which allows for excellent layering of video objects on top of each other in the HTML DOM, in real time, with no noticable performance hits.

  Aside from it’s predecessor, FLV, I can’t think of another high quality, high compression codec that also supports alpha. I feel like you are stuck using pro-res 4444 or the ancient animation codec to reliable distribute video with an alpha.

  So, that said, are there technical reasons why webM isn’t more adopted than mp4 ?

  I already know the obvious, that there is dedicated hardware to decode mp4. But, is there any technicality that would prevent a hardware webM decoder ? I really want to understand more what the benefits of mp4 are over webM, which i assume is why it is more widely used than webM.

  Thanks !

• How to extract a video snippet from a video file that is being written in by ffmpeg in realtime

  31 juillet 2020, par alex.b

  At the moment i am recording a LIVE stream video from youtube with youtube-dl (https://github.com/rg3/youtube-dl)

  



  The command i use for this :

  



  youtube-dl --id -f 92 https://www.youtube.com/watch?v=VYlQJbsVs48


  



  92 is a format code that i got after executing a command to get the formats, that gave me this list :

  



  format code  extension  resolution note
140          m4a        audio only DASH audio  144k , m4a_dash container, aac  @128k (48000Hz)
141          m4a        audio only DASH audio  272k , m4a_dash container, aac  @256k (48000Hz)
160          mp4        256x144    DASH video  124k , 15fps, video only
133          mp4        426x240    DASH video  258k , 30fps, video only
134          mp4        640x360    DASH video  616k , 30fps, video only
135          mp4        854x480    DASH video 1116k , 30fps, video only
136          mp4        1280x720   DASH video 2216k , 30fps, video only
137          mp4        1920x1080  DASH video 4141k , 30fps, video only
151          mp4        72p        HLS
132          mp4        240p       HLS
92           mp4        240p       HLS
93           mp4        360p       HLS
94           mp4        480p       HLS
95           mp4        720p       HLS
96           mp4        1080p      HLS  (best)


  



  This is creating a file called VYlQJbsVs48.mp4.part that gets bigger and bigger of course.

  



  Is there a way to extract a video snippet from that live stream or form the part file ? Or maybe there is a better way of doing this ?

  



  What i have noticed is that if i force quit iTerm2 while youtube-dl is running the .part file it creates wont contain any index information (something to do with an moov atom not being present in the mp4 file - which is the information about the number of frames and other things - metadata i think), so it makes me think i cannot extract from the file.

  



  Maybe if there would be a way that youtube-dl can write the index information at all times or maybe another way that i can record the live stream and get video snippets while its recording.

  



  I forgot to mention i am doing this on OSX Yosemite. I have FFMPEG installed with homebrew and youtoube-dl

  



  I am more than happy to try stuff on UBUNTU if there is a solution.

  



  Any help would be greatly appreciated.

  



  Thank you.

  



  Alex

  


• Stacking different length videos not working with ffmpeg and -itsoffset

  3 avril 2019, par Lucas Madalozzo

  I developed a video conferencing app that records the video streams separately, and I am now looking for a way to merge them. At the moment I am experimenting with -itsoffset and hstack to stack 2 videos side by side using this command :

  ffmpeg \
  
  -itsoffset 17 -i smaller.mp4 \
  
  -itsoffset 0 -i bigger.mp4 \
  
  -filter_complex hstack=inputs=2 \
  
  -c:v libx264 -crf 23 out.mp4

  The result is a side by side video where both streams remain frozen for 17 seconds then start playing, even the bigger.mp4 video that should start at time 0.

  Any help would be really appreciated !

  ffmpeg verbose :

  ffmpeg version 4.1 Copyright (c) 2000-2018 the FFmpeg developers
  
    built with gcc 4.9.2 (Debian 4.9.2-10+deb8u1)
  
    configuration: --enable-gpl --enable-postproc --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libx264 --enable-libspeex --enab                                                                                                                                       le-shared --enable-pthreads --enable-libopenjpeg --enable-nonfree --enable-libopus --enable-libvorbis --enable-libvpx
  
    libavutil      56. 22.100 / 56. 22.100
  
    libavcodec     58. 35.100 / 58. 35.100
  
    libavformat    58. 20.100 / 58. 20.100
  
    libavdevice    58.  5.100 / 58.  5.100
  
    libavfilter     7. 40.101 /  7. 40.101
  
    libswscale      5.  3.100 /  5.  3.100
  
    libswresample   3.  3.100 /  3.  3.100
  
    libpostproc    55.  3.100 / 55.  3.100
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'smaller.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.20.100
  
    Duration: 00:00:05.16, start: 0.000000, bitrate: 444 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 480x360 [SAR 1:1 DAR 4:3], 330 kb/s, 32 fps, 32 tbr, 16384 tbn, 64 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 103 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'bigger.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf56.36.100
  
    Duration: 00:00:22.03, start: 0.000000, bitrate: 290 kb/s
  
      Stream #1:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 480x360 [SAR 1:1 DAR 4:3], 177 kb/s, 32 fps, 32 tbr, 16384 tbn, 64 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #1:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 103 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
  File 'out.mp4' already exists. Overwrite ? [y/N] y
  
  Stream mapping:
  
    Stream #0:0 (h264) -> hstack:input0 (graph 0)
  
    Stream #1:0 (h264) -> hstack:input1 (graph 0)
  
    hstack (graph 0) -> Stream #0:0 (libx264)
  
    Stream #0:1 -> #0:1 (aac (native) -> aac (native))
  
  Press [q] to stop, [?] for help
  
  [libx264 @ 0x206ed00] using SAR=1/1
  
  [libx264 @ 0x206ed00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
  
  [libx264 @ 0x206ed00] profile High, level 3.1
  
  [libx264 @ 0x206ed00] 264 - core 146 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex                                                                                                                                        subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=3 lookahead_threads=1 sliced_thre                                                                                                                                       ads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scene                                                                                                                                       cut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, mp4, to 'out.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.20.100
  
      Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 960x360 [SAR 1:1 DAR 8:3], q=-1--1, 32 fps, 16384 tbn, 32 tbc (default)
  
      Metadata:
  
        encoder         : Lavc58.35.100 libx264
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler
  
        encoder         : Lavc58.35.100 aac
  
  frame=  709 fps=130 q=-1.0 Lsize=     573kB time=00:00:22.12 bitrate= 212.2kbits/s dup=544 drop=0 speed=4.05x
  
  video:478kB audio:81kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.445685%
  
  [libx264 @ 0x206ed00] frame I:3     Avg QP:16.86  size: 38355
  
  [libx264 @ 0x206ed00] frame P:190   Avg QP:18.22  size:  1633
  
  [libx264 @ 0x206ed00] frame B:516   Avg QP:16.23  size:   123
  
  [libx264 @ 0x206ed00] consecutive B-frames:  1.3%  2.8%  6.8% 89.1%
  
  [libx264 @ 0x206ed00] mb I  I16..4:  6.6% 54.8% 38.6%
  
  [libx264 @ 0x206ed00] mb P  I16..4:  0.4%  1.5%  0.2%  P16..4:  8.7%  4.0%  1.9%  0.0%  0.0%    skip:83.3%
  
  [libx264 @ 0x206ed00] mb B  I16..4:  0.0%  0.1%  0.0%  B16..8:  4.2%  0.3%  0.0%  direct: 0.0%  skip:95.4%  L0:37.2% L1:58.9% BI: 4.0%
  
  [libx264 @ 0x206ed00] 8x8 transform intra:66.2% inter:63.4%
  
  [libx264 @ 0x206ed00] coded y,uvDC,uvAC intra: 66.1% 65.6% 21.6% inter: 1.7% 1.1% 0.0%
  
  [libx264 @ 0x206ed00] i16 v,h,dc,p: 21% 26% 11% 42%
  
  [libx264 @ 0x206ed00] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 23% 13%  5%  7%  8%  7%  7%  6%
  
  [libx264 @ 0x206ed00] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 28% 24%  9%  6%  7%  7%  6%  7%  7%
  
  [libx264 @ 0x206ed00] i8c dc,h,v,p: 46% 25% 20%  9%
  
  [libx264 @ 0x206ed00] Weighted P-Frames: Y:1.1% UV:0.0%
  
  [libx264 @ 0x206ed00] ref P L0: 66.0% 19.4% 12.0%  2.6%  0.0%
  
  [libx264 @ 0x206ed00] ref B L0: 87.2% 11.8%  1.0%
  
  [libx264 @ 0x206ed00] ref B L1: 95.2%  4.8%
  
  [libx264 @ 0x206ed00] kb/s:176.52
  
  [aac @ 0x204aa00] Qavg: 247.398