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• ffmpeg way to encode h265 video that allows fast-forward play without jumps

  27 octobre 2022, par SysHex

  Let me start of by saying that this issue presents itself on a Android headset, while running a Unity app with unity video player component that plays a video on it at 2 times the speed. Hence, the issue might be related to these components and not the video file itself.

  


  I have a library of video files with properties as I will describe further down this post.

  


  When I play these files at 2x the speed , the become extremelly jumpy to the point they can't be watched.

  


  I've played with configurations such as : min-keyint=30:keyint=30:scenecut=0:open-gop=0:lossless=1 but I have to be honest and state that I have almost no clue as to what they do. I've read the documentation and understand gop, I-Frames , and the need to exist reference frames for fast seek, and almost for sure Fast playing of the file (?! maybe not ?) , but don't know how to fine tune this.

  


  Maybe I'm missing out something completely and/or someone as any advice as to what I could try ?

  


  The goal is to play these files at 2x its speed, or possibly faster.

  


  Now for the details on the mpeg4 files :

  


  Video
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main@L5@Main
Codec ID                                 : hev1
Codec ID/Info                            : High Efficiency Video Coding
Duration                                 : 15 min 0 s
Bit rate                                 : 6 578 kb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 30.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0 (Type 0)
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.026
Stream size                              : 706 MiB (98%)
Writing library                          : x265 3.5+37-07b011400:[Windows][GCC 11.2.0][64 bit] 8bit+10bit+12bit
Encoding settings                        : cpuid=1111039 / frame-threads=3 / numa-pools=8 / wpp / no-pmode / no-pme / no-psnr / no-ssim / log-level=2 / input-csp=1 / input-res=3840x2160 / interlace=0 / total-frames=0 / level-idc=0 / high-tier=1 / uhd-bd=0 / ref=4 / no-allow-non-conformance / no-repeat-headers / annexb / no-aud / no-eob / no-eos / no-hrd / info / hash=0 / no-temporal-layers / open-gop / min-keyint=25 / keyint=250 / gop-lookahead=0 / bframes=4 / b-adapt=2 / b-pyramid / bframe-bias=0 / rc-lookahead=25 / lookahead-slices=4 / scenecut=40 / no-hist-scenecut / radl=0 / no-splice / no-intra-refresh / ctu=64 / min-cu-size=8 / rect / no-amp / max-tu-size=32 / tu-inter-depth=1 / tu-intra-depth=1 / limit-tu=0 / rdoq-level=2 / dynamic-rd=0.00 / no-ssim-rd / signhide / no-tskip / nr-intra=0 / nr-inter=0 / no-constrained-intra / strong-intra-smoothing / max-merge=3 / limit-refs=3 / limit-modes / me=3 / subme=3 / merange=57 / temporal-mvp / no-frame-dup / no-hme / weightp / no-weightb / no-analyze-src-pics / deblock=0:0 / sao / no-sao-non-deblock / rd=4 / selective-sao=4 / no-early-skip / rskip / no-fast-intra / no-tskip-fast / no-cu-lossless / no-b-intra / no-splitrd-skip / rdpenalty=0 / psy-rd=2.00 / psy-rdoq=1.00 / no-rd-refine / no-lossless / cbqpoffs=0 / crqpoffs=0 / rc=crf / crf=20.0 / qcomp=0.60 / qpstep=4 / stats-write=0 / stats-read=0 / ipratio=1.40 / pbratio=1.30 / aq-mode=2 / aq-strength=1.00 / cutree / zone-count=0 / no-strict-cbr / qg-size=32 / no-rc-grain / qpmax=69 / qpmin=0 / no-const-vbv / sar=0 / overscan=0 / videoformat=5 / range=0 / colorprim=1 / transfer=1 / colormatrix=1 / chromaloc=1 / chromaloc-top=0 / chromaloc-bottom=0 / display-window=0 / cll=0,0 / min-luma=0 / max-luma=255 / log2-max-poc-lsb=8 / vui-timing-info / vui-hrd-info / slices=1 / no-opt-qp-pps / no-opt-ref-list-length-pps / no-multi-pass-opt-rps / scenecut-bias=0.05 / hist-threshold=0.03 / no-opt-cu-delta-qp / no-aq-motion / no-hdr10 / no-hdr10-opt / no-dhdr10-opt / no-idr-recovery-sei / analysis-reuse-level=0 / analysis-save-reuse-level=0 / analysis-load-reuse-level=0 / scale-factor=0 / refine-intra=0 / refine-inter=0 / refine-mv=1 / refine-ctu-distortion=0 / no-limit-sao / ctu-info=0 / no-lowpass-dct / refine-analysis-type=0 / copy-pic=1 / max-ausize-factor=1.0 / no-dynamic-refine / no-single-sei / no-hevc-aq / no-svt / no-field / qp-adaptation-range=1.00 / scenecut-aware-qp=0conformance-window-offsets / right=0 / bottom=0 / decoder-max-rate=0 / no-vbv-live-multi-pass
Language                                 : English
Color range                              : Limited
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : hvcC

Audio
ID                                       : 2
Format                                   : AAC LC
Format/Info                              : Advanced Audio Codec Low Complexity
Codec ID                                 : mp4a-40-2
Duration                                 : 15 min 0 s
Source duration                          : 15 min 0 s
Source_Duration_LastFrame                : -12 ms
Bit rate mode                            : Constant
Bit rate                                 : 128 kb/s
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 48.0 kHz
Frame rate                               : 46.875 FPS (1024 SPF)
Compression mode                         : Lossy
Stream size                              : 13.8 MiB (2%)
Source stream size                       : 13.8 MiB (2%)
Default                                  : Yes
Alternate group                          : 1
mdhd_Duration                            : 900233



  


• libavformat : Improve ff_configure_buffers_for_index for excessive deltas

  21 mars 2023, par Martin Storsjö

  libavformat : Improve ff_configure_buffers_for_index for excessive deltas
  Previously, the ff_configure_buffers_for_index function had
  
  upper sanity limits of 16 MB (1<<24) for buffer_size and
  
  8 MB (1<<23) for short_seek_threshold.
  However, if the index contained entries with a much larger
  
  delta, setting pos_delta to a value larger than the sanity
  
  limit, we would end up not increasing the buffer size at all.
  Instead, ignore the individual deltas that are excessive, but
  
  increase the buffer size based on the deltas that are below the
  
  sanity limit.
  Only count deltas that are below 1<<23, 8 MB ; pos_delta gets doubled
  
  before setting the buffer size - this matches the previous maximum
  
  buffer size of 1<<24, 16 MB.
  This can happen e.g. with a mov file with some tracks containing
  
  some samples that belong in the start of the file, at the end of
  
  the mdat, while the rest of the file is mostly reasonably interleaved ;
  
  previously those samples caused the maximum pos_delta to skyrocket,
  
  skipping any buffer size enlargement.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavformat/seek.c

• Decode demuxed frames produced by ffmpeg wasm using webcodecs

  10 février 2024, par Przemek Gałęzki

  Im trying to use webcodecs VideoDecoder to decode frames demuxed by ffmpeg wasm, but it doesnt seem as straightforward like when I've used mp4boxjs which provides you with necessary data for each demuxed chunk to provide to decode(), or I just dont know how to use ffmpeg wasm to properly extract chunk data

  


  so my questions are :

  


  

  • how do I properly split whole demuxed file into chunks so that I can then provide those to EncodedVideoChunk ?

  


  • after I have those split, for each EncodedVideoChunk I also need to provide it with

    

    • timestamp, not sure if performance.now is all right or not ?

    


    • data, probably just buffer source of chunk — after i get those right

    


    • type, which is either key or delta, no idea when should be which

    


    • duration

    


    


  


  


  I also need to configure decoder, ive used ffprobe-wasm here, but it doesnt provide exact codec name and description.
Even if i know exacly whats the codec name and demux my mp4 video to annexb format which if im correct doesnt need description, im getting error : A key frame is required after configure or flush and that i need to fill out the description field anyways.
I will be happy to get some insights, it seems like a lot to dig into to get it working ..