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• Ffmpeg inaccurate cut duration with ts [duplicate]

  30 juillet 2020, par Lemon Sky

  I need to accurately seek and cut a video. Some online sources say put -ss in front or after the source. The result is the same for me. In the examples below, the start time is accurate but the duration is not accurate.

  


  ffmpeg -y -ss 00:00:05 -t 00:00:05 -i http://tyberis.com/output.ts 5s.wav
ffprobe 5s.wav

Duration: 00:00:04.74

ffmpeg -y -i http://tyberis.com/output.ts -ss 00:00:05 -t 00:00:05 5s.wav
ffprobe 5s.wav

Duration: 00:00:04.74


  


  Sometimes the starting point is not accurate but the duration is. This is clearly audible by cutting the ts file and cutting an uncompressed wav file, and listening to both.

  


  ffmpeg -y -i http://tyberis.com/output.ts -ss 00:00:15 -t 00:00:05 5s.wav

ffmpeg -y -i http://tyberis.com/output.wav -ss 00:00:15 -t 00:00:05 5s-reference.wav


  


  What fixes the starting time is if I use an m3u8 file that contains the byte offset for every keyframe AND I put the -ss option in front of the source file (if I put it after the source, the start time is inaccurate but the duration is accurate) :

  


  ffmpeg -y -ss 00:00:15 -t 00:00:05 -i http://tyberis.com/output.m3u8 5s.wav


  


  This fixes the start time but the duration is at the location that I would get had I used no m3u8 file (duration is just 4.47s).

  


  It seems different timestamps are involved, and sometimes one or the other gets used.

  


  The ts file was generated by capturing a UDP stream and storing it with ffmpeg and -codec:v copy.

  


  Is ffmpeg broken, or the ts file ? How do I work around this issue or fix the ts file ? What I realize is that the video starts later than the audio, probably because the video does not start with a keyframe. Can I get ffmpeg to start the -codec:v copy after the first keyframe ? What I also notice is that using ffprobe reports "start : 1.400000". Can I force it to start at 0 ?

  


  Any hints would be appreciated.

  


  I tried both ffmpeg 4.3.1 and ffmpeg git-2020-07-24-21442a8.

  


• Ffmpeg inaccurate cutting with ts and m3u8 files despite resamping audio filter

  31 juillet 2020, par Lemon Sky

  I need to accurately seek and cut a video. Some online sources say put -ss in front or after the source. The result is the same for me. In the examples below, the start time is accurate but the duration is not accurate.

  


  ffmpeg -y -ss 00:00:05 -t 00:00:05 -i output.ts 5s.wav
ffprobe 5s.wav

Duration: 00:00:04.74

ffmpeg -y -i output.ts -ss 00:00:05 -t 00:00:05 5s.wav
ffprobe 5s.wav

Duration: 00:00:04.74


  


  Sometimes the starting point is not accurate but the duration is. This is clearly audible by cutting the ts file and cutting an uncompressed wav file, and listening to both.

  


  ffmpeg -y -i output.ts -ss 00:00:15 -t 00:00:05 5s.wav

ffmpeg -y -i output.wav -ss 00:00:15 -t 00:00:05 5s-reference.wav


  


  What fixes the starting time is if I use an m3u8 file that contains the byte offset for every keyframe AND I put the -ss option in front of the source file (if I put it after the source, the start time is inaccurate but the duration is accurate) :

  


  ffmpeg -y -ss 00:00:15 -t 00:00:05 -i output.m3u8 5s.wav


  


  This fixes the start time but the duration is at the location that I would get had I used no m3u8 file (duration is just 4.47s).

  


  It seems different timestamps are involved, and sometimes one or the other gets used.

  


  The ts file was generated by capturing a UDP stream and storing it with ffmpeg and -codec:v copy.

  


  Is ffmpeg broken, or the ts file ? How do I work around this issue or fix the ts file ? What I realize is that the video starts later than the audio, probably because the video does not start with a keyframe. Can I get ffmpeg to start the -codec:v copy after the first keyframe ? What I also notice is that using ffprobe reports "start : 1.400000". Can I force it to start at 0 ?

  


  Any hints would be appreciated.

  


  I tried both ffmpeg 4.3.1 and ffmpeg git-2020-07-24-21442a8.

  


  The output.* files were generated as follows. The statement "af aresample=async=1" should fill missing audio according to Duration of source video and subtracted audio are different. Adding this statement makes no difference in terms of accuracy or duration. The question is not a duplicate.

  


  ffmpeg -i udp://example:port ^
-af aresample=async=1 ^
-codec:v copy ^
-codec:a aac -ac 2 -ar 44100 -b:a 160k ^
-hls_time 4 -hls_flags single_file -hls_list_size 0 -hls_segment_filename output.ts -hls_segment_type mpegts output.m3u8 ^
-codec:a pcm_s16le -bitexact -ar 11025 -ac 1 output.wav


  


• how to make ffmpeg transcoding from mjpeg to h264 in real time ?

  3 août 2020, par SolskGaer

  I have a mjpeg stream which output picture 10FPS(cellphone screenshot), and I use the following command to trancode it to a h264 stream and play it on my laptop

  


  ffmpeg -f mjpeg -r 20 -y -i http://127.0.0.1:53293/  -vcodec libx264 -preset veryfast -profile:v baseline -b:v 1024k -r 10 -f h264 pipe:1 | ffplay -i pipe:0


  


  but the output stream is a few seconds behind the cellphone screen. Here is the output of ffmpeg

  


  ffplay version 4.3.1 Copyright (c) 2003-2020 the FFmpeg developers
  built with Apple clang version 11.0.3 (clang-1103.0.32.62)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1 --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-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --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
ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with Apple clang version 11.0.3 (clang-1103.0.32.62)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1 --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-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --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. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, mjpeg, from 'http://127.0.0.1:53293/':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: mjpeg (Baseline), yuvj420p(pc, bt470bg/unknown/unknown), 750x1334 [SAR 144:144 DAR 375:667], 20 tbr, 1200k tbn, 20 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x7f8f2900da00] using SAR=1/1
[libx264 @ 0x7f8f2900da00] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7f8f2900da00] profile Constrained Baseline, level 3.2, 4:2:0, 8-bit
Output #0, h264, to 'pipe:1':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: h264 (libx264), yuvj420p(pc), 750x1334 [SAR 144:144 DAR 375:667], q=-1--1, 1024 kb/s, 10 fps, 10 tbn, 10 tbc
    Metadata:
      encoder         : Lavc58.91.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/1024000 buffer size: 0 vbv_delay: N/A
frame=   30 fps=5.2 q=29.0 size=      97kB time=00:00:00.10 bitrate=7911.0kbits/s dup=0 drop=26 speed=0.0172
frame=   33 fps=5.2 q=41.0 size=     190kB time=00:00:00.40 bitrate=3888.2kbits/s dup=0 drop=29 speed=0.0633
frame=   35 fps=5.1 q=40.0 size=     253kB time=00:00:00.60 bitrate=3457.8kbits/s dup=0 drop=31 speed=0.0874
frame=   38 fps=5.1 q=40.0 size=     330kB time=00:00:00.90 bitrate=3006.1kbits/s dup=0 drop=34 speed=0.122x
frame=   40 fps=5.1 q=40.0 size=     381kB time=00:00:01.10 bitrate=2838.3kbits/s dup=0 drop=36 speed=0.139x
frame=   43 fps=5.1 q=39.0 size=     460kB time=00:00:01.40 bitrate=2691.3kbits/s dup=0 drop=39 speed=0.166x
frame=   45 fps=5.0 q=39.0 size=     505kB time=00:00:01.60 bitrate=2585.9kbits/s dup=0 drop=41 speed=0.178x
frame=   48 fps=5.0 q=38.0 size=     552kB time=00:00:01.90 bitrate=2381.0kbits/s dup=0 drop=44 speed= 0.2x 
frame=   50 fps=5.0 q=33.0 size=     562kB time=00:00:02.10 bitrate=2190.7kbits/s dup=0 drop=46 speed=0.209x
frame=   53 fps=5.0 q=37.0 size=     572kB time=00:00:02.40 bitrate=1951.2kbits/s dup=0 drop=49 speed=0.227x
frame=   55 fps=5.0 q=37.0 size=     581kB time=00:00:02.60 bitrate=1830.0kbits/s dup=0 drop=51 speed=0.234x
frame=   58 fps=5.0 q=36.0 size=     591kB time=00:00:02.90 bitrate=1670.8kbits/s dup=0 drop=54 speed=0.25x 
frame=   60 fps=4.9 q=35.0 size=     598kB time=00:00:03.10 bitrate=1580.2kbits/s dup=0 drop=56 speed=0.255x
frame=   63 fps=5.0 q=35.0 size=     608kB time=00:00:03.40 bitrate=1465.2kbits/s dup=0 drop=59 speed=0.268x
frame=   65 fps=4.9 q=34.0 size=     613kB time=00:00:03.60 bitrate=1395.7kbits/s dup=0 drop=61 speed=0.273x
frame=   68 fps=5.0 q=34.0 size=     659kB time=00:00:03.90 bitrate=1384.5kbits/s dup=0 drop=64 speed=0.284x
frame=   70 fps=4.9 q=34.0 size=     682kB time=00:00:04.10 bitrate=1363.2kbits/s dup=0 drop=66 speed=0.288x
frame=   73 fps=4.9 q=35.0 size=     720kB time=00:00:04.40 bitrate=1340.1kbits/s dup=0 drop=69 speed=0.298x
frame=   75 fps=4.9 q=35.0 size=     746kB time=00:00:04.60 bitrate=1329.1kbits/s dup=0 drop=71 speed=0.301x
frame=   78 fps=4.9 q=36.0 size=     786kB time=00:00:04.90 bitrate=1314.6kbits/s dup=0 drop=74 speed=0.31x 
frame=   80 fps=4.9 q=36.0 size=     811kB time=00:00:05.10 bitrate=1303.3kbits/s dup=0 drop=76 speed=0.312x


  


  I don't think the CPU of my laptop is the bottleneck of this process, here is the spec of my laptop

  


  
      Model Name: MacBook Pro
      Model Identifier: MacBookPro16,1
      Processor Name: 6-Core Intel Core i7
      Processor Speed: 2.6 GHz
      Number of Processors: 1
      Total Number of Cores: 6
      L2 Cache (per Core): 256 KB
      L3 Cache: 12 MB
      Hyper-Threading Technology: Enabled
      Memory: 16 GB


  


  but I can't track the reason why this happened. What can I make the output stream be real time ? Any suggestion would be appreciated.