Recherche avancée

Sur d’autres sites (7034)

• On the fly transcoding and HLS streaming with ffmpeg

  12 janvier 2023, par syfluqs

  I am building a web application that involves serving various kinds of video content. Web-friendly audio and video codecs are handled without any problems, but I am having trouble designing the delivery of video files incompatible with HTML5 video players like mkv containers or H265.

  



  What I have done till now, is use ffmpeg to transcode the video file on the server and make HLS master and VOD playlists and use hls.js on the frontend. The problem, however, is that ffmpeg treats the playlist as a live stream playlist until transcoding is complete on the whole file and then it changes the playlist to serve as VOD. So, the user can't seek until the transcoding is over, and that my server has unnecessarily transcoded the whole file if the user decides to seek the video file halfway ahead. I am using the following ffmpeg command line arguments

  



  ffmpeg -i sample.mkv \
       -c:v libx264 \
       -crf 18 \
       -preset ultrafast \
       -maxrate 4000k \
       -bufsize 8000k \
       -vf "scale=1280:-1,format=yuv420p" \
       -c:a copy -start_number 0 \
       -hls_time 10 \
       -hls_list_size 0 \
       -f hls \
file.m3u8


  



  Now to improve upon this system, I tried to generate the VOD playlist through my app and not ffmpeg, since the format is self explanatory. The webapp would generate the HLS master and VOD playlists beforehand using the video properties such as duration, resolution and bitrate (which are known to the server) and serve the master playlist to the client. The client then starts requesting the individual video segments at which point the server will individually transcode and generate each segment and serve them. Seeking would be possible as the client already has the complete VOD playlist and it can request the specific segment that the user seeks to. The benefit, as I see it, would be that my server would not have to transcode the whole file, if the user decides to seek forward and play the video halfway through.

  



  Now I tried manually creating segments (10s each) from my sample.mkv using the following command

  



  ffmpeg -ss 90 \
       -t 10 \
       -i sample.mkv \
       -g 52 \
       -strict experimental \
       -movflags +frag_keyframe+separate_moof+omit_tfhd_offset+empty_moov \
       -c:v libx264 \
       -crf 18 \
       -preset ultrafast \
       -maxrate 4000k \
       -bufsize 8000k \
       -vf "scale=1280:-1,format=yuv420p" \
       -c:a copy \
fileSequence0.mp4


  



  and so on for other segments, and the VOD playlist as

  



  #EXTM3U
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-TARGETDURATION:10
#EXT-X-VERSION:4
#EXT-X-MEDIA-SEQUENCE:0
#EXTINF:10.0,
fileSequence0.mp4
#EXTINF:10.0,
fileSequence1.mp4
...
... and so on 
...
#EXT-X-ENDLIST


  



  which plays the first segment just fine but not the subsequent ones.

  



  Now my questions,

  



  


  1. Why don't the subsequent segments play ? What am I doing wrong ?

  


  2. Is my technique even viable ? Would there be any problem with presetting the segment durations since segmenting is only possible after keyframes and whether ffmpeg can get around this ?

  


  



  My knowledge regarding video processing and generation borders on modest at best. I would greatly appreciate some pointers.

  


• FFMPEG Transcode H265 video from 10-bit to 8-bit

  6 juin 2020, par Zach

  I'm trying to convert my library from various formats into HEVC 8-bit mainly to shrink my library down. This is generally working but I've run into an issue when trying to convert an existing file from 10-bit H.265 to 8-bit H.265.

  



  My processor, an Intel Celeron J3455, supports hardware decoding/encoding H.265 at 8-bit but only hardware decoding for 10-bit.

  



  It seems that ffmpeg is attempting to keep the video as 10-bit to match the source rather than allowing me to convert to 8-bit and this is creating an error.

  



  Here is a sample command that I'm using :

  



  ffmpeg -hwaccel vaapi -hwaccel_device /dev/dri/renderD128 -hwaccel_output_format vaapi -i input.10bit.x265.mkv -map 0:0 -c:v:0 hevc_vaapi -vf "scale_vaapi=w=-1:h=1080" -b:v 4027047 -map 0:1 -c:a:0 aac -b:a 384000 -ac 6 -map 0:s -scodec copy -map_metadata:g -1 -metadata JBDONEVERSION=1 -metadata JBDONEDATE=2020-06-06T20:52:36.072Z -map_chapters 0 output.8bit.x265.mkv

  



  The error I get is :

  



  [hevc_vaapi @ 0x5568b27fb1c0] No usable encoding entrypoint found for profile VAProfileHEVCMain10 (18).

Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height


  



  From what I can tell ffmpeg looks at the source and selectes VAProfileHEVCMain10 instead of VAProfileHEVCMain. I'd like to force it to output 8-bit.

  



  I've tried adding -pix_fmt yuv420p but that gives me this error :

  



  Incompatible pixel format 'yuv420p' for codec 'hevc_vaapi', auto-selecting format 'vaapi_vld' 


  



  I've also tried making this change to the command : "scale_vaapi=w=-1:h=1080,format=yuv420p"

  



  However that gives me the error :

  



  Impossible to convert between the formats supported by the filter 'Parsed_scale_vaapi_0' and the filter 'auto_scaler_0'

Error reinitializing filters!


  



  Any suggestions ?

  


• lavf/chromaprint : Silence compilation warnings

  13 août 2019, par Carl Eugen Hoyos

  lavf/chromaprint : Silence compilation warnings
  Fixes the following warnings :
  
  libavformat/chromaprint.c:117:42 : warning : passing argument 2 of ‘chromaprint_feed’ from incompatible pointer type
  
  libavformat/chromaprint.c:132:52 : warning : passing argument 2 of ‘chromaprint_get_raw_fingerprint’ from incompatible pointer type
  
  libavformat/chromaprint.c:143:71 : warning : passing argument 4 of ‘chromaprint_encode_fingerprint’ from incompatible pointer type
  

  • [DH] libavformat/chromaprint.c