Recherche avancée

Sur d’autres sites (10134)

• Transcode HLS Segments individually using FFMPEG

  27 mai 2013, par rayh

  I am recording a continuous, live stream to a high-bitrate HLS stream. I then want to asynchronously transcode this to different formats/bitrates. I have this working, mostly, except audio artefacts are appearing between each segment (gaps and pops).

  Here is an example ffmpeg command line :

  ffmpeg -threads 1 -nostdin -loglevel verbose \
  
     -nostdin -y -i input.ts -c:a libfdk_aac \
  
     -ac 2 -b:a 64k -y -metadata -vn output.ts

  Inspecting an example sound file shows that there is a gap at the end of the audio :

  

  And the start of the file looks suspiciously attenuated (although this may not be an issue) :

  

  My suspicion is that these artefacts are happening because transcoding are occurring without the context of the stream as a whole.

  Any ideas on how to convince FFMPEG to produce audio that will fit back into a HLS stream ?

  ** UPDATE 1 **

  Here are the start/end of the original segment. As you can see, the start still appears the same, but the end is cleanly ended at 30s. I expect some degree of padding with lossy encoding, but I there is some way that HLS manages to do gapless playback (is this related to iTunes method with custom metadata ?)

  
  

  ** UPDATED 2 **

  So, I converted both the original (128k aac in MPEG2 TS) and the transcoded (64k aac in aac/adts container) to WAV and put the two side-by-side. This is the result :

  
  

  I'm not sure if this is representative of how a client will play it back, but it seems a bit odd that decoding the transcoded one introduces a gap at the start and makes the segment longer. Given they are both lossy encoding, I would have expected padding to be equally present in both (if at all).

  ** UPDATE 3 **

  According to http://en.wikipedia.org/wiki/Gapless_playback - Only a handful of encoders support gapless - for MP3, I've switched to lame in ffmpeg, and the problem, so far, appears to have gone.

  For AAC (see http://en.wikipedia.org/wiki/FAAC), I have tried libfaac (as opposed to libfdk_aac) and it also seems to produce gapless audio. However, the quality of the latter isn't that great and I'd rather use libfdk_aac is possible.

• Documentation #2739 (Fermé) : Doc des API édition d’objet et job_queue

  7 septembre 2012, par cedric -

  je ferme car c’est plus généralement la taskforce documentation qui redispatchera les docs

• Anomalie #4820 : Double chargement des css

  15 juin 2021

  C’est du à Firefox et au header Link envoyé oui.
  C’est hyper désagréable en debug dans Firefox.

  Refs :
  - https://developer.mozilla.org/fr/docs/Web/HTTP/Link_prefetching_FAQ
  - https://www.w3.org/TR/resource-hints/

  Symfony fait ça avec le composant Web Link :
  - https://github.com/symfony/web-link
  - https://symfony.com/doc/current/web_link.html

  Il faudrait regarder si : sf enlève la balise `` ou pas (je ne pense pas) du html et/ou si ça se comporte pareil dans FF et pourquoi sinon.