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• ffmpeg hwo to choose the best bit rate for HLS streaming ?

  7 février 2023, par Josef Kranz

  I'm building a video streaming white label product, but I've run into the following scenario where I'm not sure what might be the optimal way to get the best video quality in return. At the moment I'm using crf based encoding, which is from a streaming based point of view a very bad idea. From a quality point of view, it will definitely give me the best quality and also the best efficiency. Why is crf based encoding bad for streaming ? First you have a non-fixed file size, meaning your bit rate might vary between 20 kbps and 20 Mbit/s depending on the codec and picture motion of the current frames ...
When you have such heavily varying stream according to the bit rate, automatic quality selection at the player might not function correctly, and the player automatically switches from 1080p to 480p for no reason (using VideoJS here).

  


  To fix this issue, it's fine if I set minrate, maxrate with ffmpeg but this will also come at the cost that some frames might look pixelated, which I absolutely do not want.

  


  Currently, my encoding command looks something like this :

  


  /usr/bin/ffmpeg -i "/tmp/VODProcessing/Tester 2160p UHD-HDR.mp4" -map 0:0 -c:v libsvtav1 -crf 19 -vf zscale=width=3840:height=2160 -svtav1-params "profile=0:enable-force-key-frames=1:superres-mode=1:enable-tf=0:tune=0:enable-overlays=1:scd=1:scm=2:enable-mfmv=1:enable-cdef=1:enable-dlf=1:fast-decode=1:color-primaries=9:transfer-characteristics=16:matrix-coefficients=9:input-depth=10:mastering-display=G(0.265,0.69)B(0.15,0.06)R(0.68,0.32)WP(0.3127,0.329)L(4000.0,0.005):content-light=368,226:enable-hdr=1:color-range=1" -pix_fmt yuv420p10le -color_trc smpte2084 -color_primaries bt2020 -colorspace bt2020nc -chroma_sample_location:v topleft -color_range:v pc -max_muxing_queue_size 1024 -preset 7 -bf 0 -force_key_frames "expr:gte(t,n_forced*4.004)" -keyint_min 48 -sc_threshold 0 -use_timeline 1 -use_template 1 -map_metadata -1 -map_chapters -1 -f hls -seg_duration 4.004 -hls_time 4.004 -streaming 1 -hls_list_size 0 -hls_segment_filename "/tmp/VODProcessing/output/Tester 2160p UHD-HDR/v-av01-2160p-av01.0.12M.10_PQ/f-%04d.m4s"  -hls_fmp4_init_filename "init-v-av01-2160p-av01.0.12M.10_PQ.m4s"  -hls_segment_type fmp4 -hls_playlist_type vod -movflags frag_keyframe+frag_every_frame+write_colr+prefer_icc+skip_trailer+faststart -hls_flags independent_segments -strict experimental "/tmp/VODProcessing/output/Tester 2160p UHD-HDR/v-av01-2160p-av01.0.12M.10_PQ/master.m3u8"


  


  Which will form a stream made out of independent m4s segments. As you can see, I'm using libsvtav1 in crf mode to output the result in AV1.

  


  Now my question is, how can I have the same nice quality output as with the crf mode while having a static/fixed bit rate ? Will 2 pass encoding solve this problem by distributing the pixels or data rate differently ?

  


  Thanks in advance

  


• How do I create an HLS master playlist with ffmpeg ?

  15 février 2023, par frankenstein

  There is a command that generates hls videos in different sizes.
Now I need to merge them into one master playlist. (What is a master playlist) How do I do this ? What and where do I need to add in this command ?

  


  ffmpeg -hide_banner -y -i input.mp4 \
  -vf scale=w=640:h=360:force_original_aspect_ratio=decrease -c:a aac -ar 48000 -c:v h264 -profile:v main -crf 20 -sc_threshold 0 -g 48 -keyint_min 48 -hls_time 4 -hls_playlist_type vod  -b:v 800k -maxrate 856k -bufsize 1200k -b:a 96k -hls_segment_filename output/360p_%03d.ts output/360p.m3u8 \
  -vf scale=w=842:h=480:force_original_aspect_ratio=decrease -c:a aac -ar 48000 -c:v h264 -profile:v main -crf 20 -sc_threshold 0 -g 48 -keyint_min 48 -hls_time 4 -hls_playlist_type vod -b:v 1400k -maxrate 1498k -bufsize 2100k -b:a 128k -hls_segment_filename output/480p_%03d.ts output/480p.m3u8 \
  -vf scale=w=1280:h=720:force_original_aspect_ratio=decrease -c:a aac -ar 48000 -c:v h264 -profile:v main -crf 20 -sc_threshold 0 -g 48 -keyint_min 48 -hls_time 4 -hls_playlist_type vod -b:v 2800k -maxrate 2996k -bufsize 4200k -b:a 128k -hls_segment_filename output/720p_%03d.ts output/720p.m3u8 \
  -vf scale=w=1920:h=1080:force_original_aspect_ratio=decrease -c:a aac -ar 48000 -c:v h264 -profile:v main -crf 20 -sc_threshold 0 -g 48 -keyint_min 48 -hls_time 4 -hls_playlist_type vod -b:v 5000k -maxrate 5350k -bufsize 7500k -b:a 192k -hls_segment_filename output/1080p_%03d.ts output/1080p.m3u8


  


  What I am interested in is the automatic creation of a master playlist using ffmpeg in this command.

  


  UPD : I answered my own question

  


  After several attempts, I still got the desired result. I modified the command and now it looks like this

  


  ffmpeg -hide_banner -re -i input.mp4 -map 0:v:0 -map 0:a:0 -map 0:v:0 -map 0:a:0 -map 0:v:0 -map 0:a:0 -map 0:v:0 -map 0:a:0 \
  -c:v h264 -profile:v main -crf 20 -sc_threshold 0 -g 48 -keyint_min 48 -c:a aac -ar 48000 \
  -filter:v:0 scale=w=640:h=360:force_original_aspect_ratio=decrease -maxrate:v:0 856k -bufsize:v:0 1200k -b:a:0 96k \
  -filter:v:1 scale=w=842:h=480:force_original_aspect_ratio=decrease -maxrate:v:1 1498k -bufsize:v:1 2100k -b:a:1 128k \
  -filter:v:2 scale=w=1280:h=720:force_original_aspect_ratio=decrease -maxrate:v:2 2996k -bufsize:v:2 4200k -b:a:2 128k \
  -filter:v:3 scale=w=1920:h=1080:force_original_aspect_ratio=decrease -maxrate:v:3 5350k -bufsize:v:3 7500k -b:a:3 192k \
  -var_stream_map "v:0,a:0 v:1,a:1 v:2,a:2 v:3,a:3" \
  -hls_time 4 \
  -hls_list_size 0 \
  -master_pl_name master.m3u8 \
  -hls_segment_filename output/%v_%03d.ts output/%v.m3u8


  


• Encoding video for PS4 Pro using ffmpeg

  16 février 2023, par Calum J Craig

  I'm trying to encode video to watch on my PS4 Pro (so want to be able to handle 4k as well as 1080p).

  


  At first I had success with the default ffmpeg .mp4 command just using this :

  


  ffmpeg -i .mkv .mp4

  


  This was fine for the first batch of 1080p videos I encoded. But, then it started to fail me - the videos would encode but when I tried to watch them on the PS4 the file would start to play with only audio, no video, play for a few seconds then fail and become unusable.

  


  I checked and apparently the PS4 requires the H.264 codec. So, I installed libx264-dev and tried :

  


  ffmpeg -i .mkv -vcodec libx264 .mp4

  


  I got the same result - the video encoded and started to play on the PS4 with only audio then failed.

  


  Any suggestions for what I am missing / doing wrong ? This is the first time for me to use ffmpeg so I am not familiar with its various features / parameters. I'm running Ubuntu 22.04.