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• ffmpeg webm to mp4 conversion failed

  13 juin 2020, par Jaunius Bumptirklu

  Trying to convert webm file to mp4. Getting "conversion failed" as a result. Other webm files I am working with converts just fine.

  



  ffprobe info on inputfile.webm

  



  $ ffprobe -v quiet -print_format json -show_format -show_streams inputfile.webm
{
    "streams": [
        {
            "index": 0,
            "codec_name": "vp8",
            "codec_long_name": "On2 VP8",
            "profile": "0",
            "codec_type": "video",
            "codec_time_base": "1/30",
            "codec_tag_string": "[0][0][0][0]",
            "codec_tag": "0x0000",
            "width": 640,
            "height": 480,
            "coded_width": 640,
            "coded_height": 480,
            "has_b_frames": 0,
            "sample_aspect_ratio": "1:1",
            "display_aspect_ratio": "4:3",
            "pix_fmt": "yuv420p",
            "level": -99,
            "field_order": "progressive",
            "refs": 1,
            "r_frame_rate": "30/1",
            "avg_frame_rate": "30/1",
            "time_base": "1/1000",
            "start_pts": 0,
            "start_time": "0.000000",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            }
        },
        {
            "index": 1,
            "codec_name": "opus",
            "codec_long_name": "Opus (Opus Interactive Audio Codec)",
            "codec_type": "audio",
            "codec_time_base": "1/48000",
            "codec_tag_string": "[0][0][0][0]",
            "codec_tag": "0x0000",
            "sample_fmt": "fltp",
            "sample_rate": "48000",
            "channels": 1,
            "channel_layout": "mono",
            "bits_per_sample": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/1000",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 12333,
            "duration": "12.333000",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0,
                "timed_thumbnails": 0
            }
        }
    ],
    "format": {
        "filename": "inputfile.webm",
        "nb_streams": 2,
        "nb_programs": 0,
        "format_name": "matroska,webm",
        "format_long_name": "Matroska / WebM",
        "start_time": "0.000000",
        "duration": "12.333000",
        "size": "1609303",
        "bit_rate": "1043900",
        "probe_score": 100,
        "tags": {
            "encoder": "Lavf56.40.101",
            "creation_time": "2020-06-12T11:32:05.000000Z"
        }
    }
}


  



  ffmpeg conversion log for command "ffmpeg -i inputfile.webm out.mp4" is below.

  



  $ ffmpeg -i inputfile.webm out.mp4
ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple clang version 11.0.3 (clang-1103.0.32.59)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2_3 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags=-fno-stack-check --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, matroska,webm, from 'inputfile.webm':
  Metadata:
    encoder         : Lavf56.40.101
    creation_time   : 2020-06-12T11:32:05.000000Z
  Duration: 00:00:12.33, start: 0.000000, bitrate: 1043 kb/s
    Stream #0:0: Video: vp8, yuv420p(progressive), 640x480, SAR 1:1 DAR 4:3, 30 fps, 30 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: opus, 48000 Hz, mono, fltp (default)
Stream mapping:
  Stream #0:0 -> #0:0 (vp8 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (opus (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x7f9e64811600] using SAR=1/1
[libx264 @ 0x7f9e64811600] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7f9e64811600] profile High, level 5.0
[libx264 @ 0x7f9e64811600] 264 - core 155 r2917 0a84d98 - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - 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=18 lookahead_threads=3 sliced_threads=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 scenecut=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
Too many packets buffered for output stream 0:0.577014:32:22.77 bitrate=  -0.0kbits/s dup=45 drop=0 speed=N/A
[libx264 @ 0x7f9e64811600] frame I:1     Avg QP:16.69  size: 56001
[libx264 @ 0x7f9e64811600] frame P:33    Avg QP:19.46  size:  9705
[libx264 @ 0x7f9e64811600] frame B:95    Avg QP:19.23  size:   662
[libx264 @ 0x7f9e64811600] consecutive B-frames:  0.8%  0.0%  4.6% 94.7%
[libx264 @ 0x7f9e64811600] mb I  I16..4: 46.7% 36.4% 16.9%
[libx264 @ 0x7f9e64811600] mb P  I16..4:  4.0%  9.4%  0.5%  P16..4:  6.5%  1.2%  0.6%  0.0%  0.0%    skip:77.8%
[libx264 @ 0x7f9e64811600] mb B  I16..4:  0.1%  0.1%  0.0%  B16..8:  6.0%  0.1%  0.0%  direct: 0.7%  skip:93.0%  L0:44.7% L1:54.8% BI: 0.4%
[libx264 @ 0x7f9e64811600] 8x8 transform intra:61.3% inter:37.9%
[libx264 @ 0x7f9e64811600] coded y,uvDC,uvAC intra: 8.6% 3.3% 1.3% inter: 0.9% 0.9% 0.1%
[libx264 @ 0x7f9e64811600] i16 v,h,dc,p: 41% 52%  6%  1%
[libx264 @ 0x7f9e64811600] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 42% 16% 41%  0%  0%  0%  0%  0%  0%
[libx264 @ 0x7f9e64811600] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 32% 40% 17%  2%  2%  2%  2%  1%  3%
[libx264 @ 0x7f9e64811600] i8c dc,h,v,p: 88%  8%  3%  0%
[libx264 @ 0x7f9e64811600] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x7f9e64811600] ref P L0: 75.5% 13.1%  9.1%  2.3%
[libx264 @ 0x7f9e64811600] ref B L0: 82.1% 16.4%  1.5%
[libx264 @ 0x7f9e64811600] ref B L1: 97.0%  3.0%
[libx264 @ 0x7f9e64811600] kb/s:816.97
Conversion failed!


  



  I don't have deeper experience with ffmpeg conversions and codecs. It seems to me that this is a frames related problem. Do you have a clue why does it fail ? What options should I use in ffmpeg command to solve this ? Thanks for any help.

  


• FFmpeg v4l2 copying unstable

  15 juin 2020, par Joel Bodenmann

  Prelude

  



  I am using ffmpeg 4.2.2 on an Ubuntu 20.04 machine to clone the feed of a USB webcam (v4l2 device as /dev/video0) so that multiple applications may access the feed. I used this ffmpeg command which worked lovely :

  



  ffmpeg -f v4l2 -i /dev/video0 -codec copy -f v4l2 /dev/video1


  



  Essentially this uses a v4l2 loopback device (dummy device) in form of /dev/video1 and a consuming application simply sees this as a regular v4l2 device.

  



  After that worked well, I ran into the need to change the output pixel format (related SO question). My source device provides yuv420p and the sink application can only deal with yuyv422. To achieve this, I use the -pix_fmt argument. This is however not supported when using -codec copy so I need to specify the codec explicitly. This is no problem as v4l2 devices only support raw video (at least as per my knowledge).
Therefore, I end up with this :

  



  ffmpeg -f v4l2 -i /dev/video0 -c:v rawvideo -pix_fmt yuyv422 -f v4l2 /dev/video1


  



  The problem

  



  Unfortunately, this appears to be very unstable. In about 1 out of 10 times of launching this command it works as expected : ffmpeg starts cloning the feed and converts the color format :

  



  joel@joel-ubuntu:~$ ffmpeg -f v4l2 -i /dev/video0 -c:v rawvideo -pix_fmt yuyv422 -f v4l2 /dev/video1
ffmpeg version 4.2.2-1ubuntu1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-3ubuntu1)
  configuration: --prefix=/usr --extra-version=1ubuntu1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
[video4linux2,v4l2 @ 0x55a4f38a5700] Time per frame unknown
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 11224.864514, bitrate: N/A
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480, 14.33 tbr, 1000k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Press [q] to stop, [?] for help
Output #0, video4linux2,v4l2, to '/dev/video1':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 640x480, q=2-31, 70451 kb/s, 14.33 fps, 14.33 tbn, 14.33 tbc
    Metadata:
      encoder         : Lavc58.54.100 rawvideo
frame=  214 fps= 15 q=-0.0 Lsize=N/A time=00:00:14.93 bitrate=N/A dup=1 drop=0 speed=1.05x    
video:128400kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.


  



  However, the other times I get very archaic behavior where the output is never usable after except for the first frame (then it freezes) and ffmpeg goes haywire mentioning over 100k duplicate frames in just a few second as well as reporting FPS way beyond 30'000. After a few seconds it then crashes or it simply hangs until I Ctrl^C it :

  



  joel@joel-ubuntu:~$ ffmpeg -f v4l2 -i /dev/video0 -c:v rawvideo -pix_fmt yuyv422 -f v4l2 /dev/video1
ffmpeg version 4.2.2-1ubuntu1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-3ubuntu1)
  configuration: --prefix=/usr --extra-version=1ubuntu1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
[video4linux2,v4l2 @ 0x561ef693c700] Time per frame unknown
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 11156.178415, bitrate: N/A
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 640x480, 1000k tbr, 1000k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> rawvideo (native))
Press [q] to stop, [?] for help
[video4linux2,v4l2 @ 0x561ef6940400] Frame rate very high for a muxer not efficiently supporting it.
Please consider specifying a lower framerate, a different muxer or -vsync 2
Output #0, video4linux2,v4l2, to '/dev/video1':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 640x480, q=2-31, 4915200000 kb/s, 1000k fps, 1000k tbn, 1000k tbc
    Metadata:
      encoder         : Lavc58.54.100 rawvideo
More than 1000 frames duplicated
More than 10000 frames duplicated
More than 100000 frames duplicated=N/A time=00:00:00.15 bitrate=N/A dup=151050 drop=0 speed=0.0456x    
27653321 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=0 speed=0.0289x    
27733577 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=1 speed=0.0256x    
27787315 frame duplication too large, skipping
27859335 frame duplication too large, skipping
27941595 frame duplication too large, skipping
28006927 frame duplication too large, skipping
28069615 frame duplication too large, skipping
28140781 frame duplication too large, skipping
28217871 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=8 speed=0.0251x    
28282039 frame duplication too large, skipping
28347777 frame duplication too large, skipping
28449099 frame duplication too large, skipping
28491015 frame duplication too large, skipping
28565585 frame duplication too large, skipping
28630457 frame duplication too large, skipping
28710537 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=15 speed=0.0247x    
28770549 frame duplication too large, skipping
28843129 frame duplication too large, skipping
28922285 frame duplication too large, skipping
28985573 frame duplication too large, skipping
29061631 frame duplication too large, skipping
29133801 frame duplication too large, skipping
29193197 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=22 speed=0.0243x    
29269443 frame duplication too large, skipping
29349681 frame duplication too large, skipping
29403629 frame duplication too large, skipping
29489299 frame duplication too large, skipping
29542137 frame duplication too large, skipping
29611859 frame duplication too large, skipping
29688271 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=29 speed=0.0238x    
29759777 frame duplication too large, skipping
29824489 frame duplication too large, skipping
29897671 frame duplication too large, skipping
29966443 frame duplication too large, skipping
30037557 frame duplication too large, skipping
30117317 frame duplication too large, skipping
30172847 frame duplication too large, skipping
30255657 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=37 speed=0.0234x    
30331325 frame duplication too large, skipping
30385245 frame duplication too large, skipping
30458209 frame duplication too large, skipping
30532393 frame duplication too large, skipping
30596453 frame duplication too large, skipping
30681671 frame duplication too large, skipping
30740757 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=44 speed=0.023x    
30806259 frame duplication too large, skipping
30873657 frame duplication too large, skipping
30950843 frame duplication too large, skipping
31013967 frame duplication too large, skipping
31099321 frame duplication too large, skipping
31172533 frame duplication too large, skipping
31224713 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=51 speed=0.0227x    
31297053 frame duplication too large, skipping
31378711 frame duplication too large, skipping
31438565 frame duplication too large, skipping
31506345 frame duplication too large, skipping
31589213 frame duplication too large, skipping
31656175 frame duplication too large, skipping
31718295 frame duplication too large, skipping
31814019 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=59 speed=0.0223x    
31876469 frame duplication too large, skipping
31917425 frame duplication too large, skipping
31995521 frame duplication too large, skipping
32062573 frame duplication too large, skipping
32127183 frame duplication too large, skipping
32197109 frame duplication too large, skipping
32267481 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=66 speed=0.022x    
32358605 frame duplication too large, skipping
32407853 frame duplication too large, skipping
32478077 frame duplication too large, skipping
32523429 frame duplication too large, skipping
32557449 frame duplication too large, skipping
32587093 frame duplication too large, skipping
32620687 frame duplication too large, skipping
32654747 frame duplication too large, skipping
32689485 frame duplication too large, skipping
32719435 frame duplication too large, skipping
32753423 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=77 speed=0.0216x    
32781827 frame duplication too large, skipping
32820747 frame duplication too large, skipping
32860855 frame duplication too large, skipping
32884671 frame duplication too large, skipping
32918767 frame duplication too large, skipping
32955299 frame duplication too large, skipping
32989505 frame duplication too large, skipping
33019757 frame duplication too large, skipping
33053493 frame duplication too large, skipping
33082955 frame duplication too large, skipping
33116965 frame duplication too large, skipping
33156613 frame duplication too large, skipping
33188409 frame duplication too large, skipping
33224915 frame duplication too large, skipping
33255715 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=92 speed=0.0213x    
33292845 frame duplication too large, skipping
33323677 frame duplication too large, skipping
33352059 frame duplication too large, skipping
33386205 frame duplication too large, skipping
33420195 frame duplication too large, skipping
33455171 frame duplication too large, skipping
33484311 frame duplication too large, skipping
33520791 frame duplication too large, skipping
33550153 frame duplication too large, skipping
33587191 frame duplication too large, skipping
33623055 frame duplication too large, skipping
33656991 frame duplication too large, skipping
33686655 frame duplication too large, skipping
33720711 frame duplication too large, skipping
33749987 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=107 speed=0.021x    
33784387 frame duplication too large, skipping
33823663 frame duplication too large, skipping
33869275 frame duplication too large, skipping
33907671 frame duplication too large, skipping
34043059 frame duplication too large, skipping
34089679 frame duplication too large, skipping
34120031 frame duplication too large, skipping
34193323 frame duplication too large, skipping
34263479 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=116 speed=0.0207x    
34403751 frame duplication too large, skipping
34470319 frame duplication too large, skipping
34542507 frame duplication too large, skipping
34613587 frame duplication too large, skipping
34687495 frame duplication too large, skipping
34755115 frame duplication too large, skipping:00:00.70 bitrate=N/A dup=707630 drop=122 speed=0.0204x    
34823847 frame duplication too large, skipping
34893931 frame duplication too large, skipping
34963903 frame duplication too large, skipping
35034011 frame duplication too large, skipping
35103715 frame duplication too large, skipping
35178691 frame duplication too large, skipping
frame=707641 fps=20090 q=-0.0 Lsize=N/A time=00:00:00.70 bitrate=N/A dup=707630 drop=129 speed=0.0201x    
video:424584600kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Exiting normally, received signal 2.


  



  I have no idea what leads to this behavior nor how to track it down & fix it. Does anybody have experience with this type of behavior or is there a simple issue on my setup ?

  



  Note : I am using DroidCam. DroidCam provides a Linux client that in turn provides a v4l2 output device. Other than a few minor hicups I did not notice any behavior that would be different from a regular webcam. Unfortunately I can't reproduce this with an ordinary USB UVC webcam as the webcam already provides the desired output pixel format. This output pixel format conversion is really just necessary because DroidCam outputs yuv420p but the application consuming the stream can only handle yuyv422.

  


• ffmpeg zero latency webcam streaming

  9 août 2022, par SimpleSimon

  I'm trying to use ffmpeg to stream a webcam with as close to zero latency as possible.

  


  My test environment is streaming from localhost to localhost, on a macOS machine.

  


  I've tried every parameter switch that I can understand - and many suggestions found both here and elsewhere. But, the latency is persistently just about one second. And to be honest, none of the options that I've tried appear to make any difference at all.

  


  I've read that it should be possible to get the latency down to a couple of hundred milliseconds - or even as low as a single video frame (in these ideal test conditions). Can anyone help me with the magic ffmpeg settings ?

  


  Here's my base ffmpeg call. Note that I've deliberately not included here any of the exotic options that might help me. I want to start fresh with this question :

  


  ffmpeg -f avfoundation -i "1:none" -vcodec libx264 -preset ultrafast -tune zerolatency -x264-params "" -f mpegts udp://127.0.0.1:9090

  


  I monitor the stream on the same machine using ffplay, with this :

  


  ffplay udp://127.0.0.1:9090

  


  My belief is that ffmpeg (and X264) are somehow buffering the input stream from the webcam during the encoding process. I know why this can be necessary. But, for the purposes of this requirement, I'm prepared to sacrifice everything in the pursuit of low latency. Quality and stability are less important.

  


  I acknowledge that there might be latency in my ffplay monitoring. I'm not so sure though - because I have tested with other monitors, with pretty much the same results. However, I'd be happy to receive advice regarding low latency monitoring.

  


  I'm assuming I'm looking for options that will encode with all i-frames, no lookahead, and no buffering. Am I right ? And if I am, how do I achieve that ?

  


  Thanks !

  


  ---

  


  Output from ffmpeg request, as per Gyan :

  


  ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2_2 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
[avfoundation @ 0x7ffbc2008a00] Selected pixel format (yuv420p) is not supported by the input device.
[avfoundation @ 0x7ffbc2008a00] Supported pixel formats:
[avfoundation @ 0x7ffbc2008a00]   uyvy422
[avfoundation @ 0x7ffbc2008a00]   yuyv422
[avfoundation @ 0x7ffbc2008a00]   nv12
[avfoundation @ 0x7ffbc2008a00]   0rgb
[avfoundation @ 0x7ffbc2008a00]   bgr0
[avfoundation @ 0x7ffbc2008a00] Overriding selected pixel format to use uyvy422 instead.
Input #0, avfoundation, from '1:none':
  Duration: N/A, start: 51270.672067, bitrate: N/A
    Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 1280x720, 17 tbr, 1000k tbn, 1000k tbc
At least one output file must be specified```


---------------------

Second output, as per second request from Gyan:

ffmpeg -f avfoundation -analyzeduration 200k -probesize 6M -pixel_format uyvy422 -i "1:none" -vcodec libx264 -preset ultrafast -tune zerolatency -x264-params "" -f mpegts udp://127.0.0.1:9090
ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2_2 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, avfoundation, from '1:none':
  Duration: N/A, start: 319.565533, bitrate: N/A
    Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 1280x720, 15 fps, 15 tbr, 1000k tbn, 1000k tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x7feda5093200] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x7feda5093200] profile High 4:2:2, level 3.1, 4:2:2 8-bit
Output #0, mpegts, to 'udp://127.0.0.1:9090':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: h264 (libx264), yuv422p, 1280x720, q=-1--1, 15 fps, 90k tbn, 15 tbc
    Metadata:
      encoder         : Lavc58.54.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame= 1209 fps= 14 q=22.0 Lsize=   65771kB time=00:01:24.13 bitrate=6404.1kbits/s speed=   1x    
video:60873kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 8.047672%
[libx264 @ 0x7feda5093200] frame I:5     Avg QP:17.80  size:142658
[libx264 @ 0x7feda5093200] frame P:1204  Avg QP:19.99  size: 51180
[libx264 @ 0x7feda5093200] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 0x7feda5093200] mb P  I16..4:  5.9%  0.0%  0.0%  P16..4: 71.8%  0.0%  0.0%  0.0%  0.0%    skip:22.3%
[libx264 @ 0x7feda5093200] coded y,uvDC,uvAC intra: 17.4% 87.8% 49.8% inter: 29.4% 74.5% 38.3%
[libx264 @ 0x7feda5093200] i16 v,h,dc,p: 57% 20% 11% 12%
[libx264 @ 0x7feda5093200] i8c dc,h,v,p: 43% 18% 27% 12%
[libx264 @ 0x7feda5093200] kb/s:6186.95
Exiting normally, received signal 2.
slartibartfast:~ simon$ ffmpeg -f avfoundation -analyzeduration 200k -probesize 6M -pixel_format uyvy422 -i "1:none" 
ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2_2 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, avfoundation, from '1:none':
  Duration: N/A, start: 421.525767, bitrate: N/A
    Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 1280x720, 14.25 tbr, 1000k tbn, 1000k tbc
At least one output file must be specified