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• FFmpeg - selecting appropriate bitrate for VP9 encoding

  6 avril 2017, par fastily

  I am looking to encode a 4k video shot with iPhone 6s in VP9 in the best quality possible.

  For reference, stream data of the video I would like to encode, via ffprobe :

  Duration: 00:00:10.48, start: 0.000000, bitrate: 46047 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 3840x2160, 45959 kb/s, 29.98 fps, 29.97 tbr, 600 tbn, 1200 tbc (default)
  
      Metadata:
  
        creation_time   : 2017-03-13T21:12:56.000000Z
  
        handler_name    : Core Media Data Handler
  
        encoder         : H.264
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 79 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-03-13T21:12:56.000000Z
  
        handler_name    : Core Media Data Handler

  I am using the following FFmpeg commands, based on these instructions (see Best Quality (Slowest) Recommended Settings section).

  1. ffmpeg -i INPUT.mov -c:v libvpx-vp9 -pass 1 -b:v 46000K -threads 4 -speed 4 -g 9999 -an -f webm -y /dev/null
  2. ffmpeg -I INPUT.mov -c:v libvpx-vp9 -pass 2 -b:v 46000K -threads 4 -speed 0 -g 9999 -an -f webm OUTPUT.webm

  Is there a best practice to select an optimal -b:v value such that the resulting video is visually indistinguishable from the original ? I have tried values ranging from 36000K-46000K, but these result in massive files with an overall bitrate exceeding the target bitrate.

  Thanks in advance !

• Converting HLS video with fmp4 segments to image thumbnails via ffmpeg with start offset using fast seek

  19 octobre 2022, par hellerahum

  I'm having trouble with what I think should be a basic use case for ffmpeg. What I'd like to do is take an hls video in fmp4 and output 30s of images at 10fps, using "fast seek" to start at an offset well into the video. This works with an Apple sample using ts segments, but not with fmp4 segments.

  


  working sample (ts)

  


  ffmpeg -ss 00:00:05 -i https://devimages.apple.com.edgekey.net/iphone/samples/bipbop/bipbopall.m3u8 -t 30 -vf fps=10 hls_samples/img%03d.jpg


  


  broken sample (fmp4)

  


  ffmpeg -ss 00:00:05 -i https://devstreaming-cdn.apple.com/videos/streaming/examples/img_bipbop_adv_example_fmp4/master.m3u8 -t 30 -vf fps=10 hls_samples/img%03d.jpg


  


  The broken sample spits out errors like :

  


  [NULL @ 0x123e30d20] Invalid NAL unit size (-2003396084 > 1673).
[NULL @ 0x123e30d20] missing picture in access unit with size 1677


  


  and then finally :

  


  Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)
Conversion failed!


  


  When I re-encode the fmp4 video adding keyframes via -g 1 (still hls with fmp4) I'm then able to use the fast seek -ss flag before the -i , but i'd rather not do this in a 2-step process, and ideally would take the original hls/fmp4 manifest and output the thumbnails directly. Both samples work with the -ss flag after the input (slow seek) but I have some long (10+ hour) videos so that's not tenable. Anyone able to point me to what I'm doing wrong, or is it possible this is an issue with ffmpeg and its support for fmp4 ? I'm using ffmpeg v5.1.2 and have checked on both an M1 mac and Ubuntu system.

  


• Why does Apple support H.265 playback, but not when using HLS ? [closed]

  13 mars, par clark wu

  Apple devices (iPhone, iPad, macOS Safari) can natively play H.265 (HEVC) videos in .mp4 or .mov format. However, when I try to convert the same video to HLS, it fails to play. Here’s what I tested :

  


  Test Cases

  


  ✅ Directly playing H.265 .mp4 → Works fine

  


  ❌ H.265 + Opus → HLS (fMP4) → Fails

  


  ❌ H.265 + AAC → HLS (TS) → Fails

  


  ✅ H.264 + Opus → HLS fMP4 → Works fine (video + audio)

  


  ✅ H.264 + Opus → HLS TS → Video plays, but no audio

  


  ❌ H.265 + AAC → HLS fMP4 → Doesn’t play at all

  


  FFmpeg Commands Used

  


  1️⃣ H.265 + Opus (fMP4 segments)

  


  ffmpeg -i input.mp4 -c:v copy -c:a copy -hls_segment_type fmp4 -hls_time 10 -hls_list_size 0 -hls_flags independent_segments output.m3u8


  


  2️⃣ H.265 + AAC (TS segments)

  


  ffmpeg -i input.mp4 -c:v copy -c:a copy -hls_time 10 -hls_list_size 0 -hls_flags independent_segments output.m3u8


  


  Playback Attempts

  


  Vidstack.js player (Fails)

  


  Several online M3U8 players (All fail)

  


  Key Questions

  


  Why does Apple support H.265 in MP4 but not in HLS ?

  


  Is this an HLS specification limitation ?

  


  Does the audio codec (Opus / AAC) affect playback ?

  


  Does HLS require a specific HEVC profile/level ?

  


  Is HLS only compatible with AVC, not HEVC ?

  


  Looking for Answers

  


  Has anyone successfully played H.265 + HLS on Apple devices ?

  


  Are there any official Apple HLS specifications regarding HEVC support ?

  


  Possible workarounds or alternative solutions ?

  


  Would appreciate any insights or help from the community ! Thanks !