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• Anomalie #4213 (Nouveau) : Installation d’un spip en reprenant une base plus récente

  2 novembre 2018, par Maïeul Rouquette

  Petit couac qui m’est arrivé tout à l’heure (en local, heureusement).

  J’install un SPIP 3.1

  Au moment de la déclaration de base, je me trompe et au lieu de lui dire de créer une nouvelle base, je lui dit de reprendre une base existante. Or cette base était en SPIP 3.2

  SPIP reprend les données de la base MAIS change le spip_version_base.

  A mon avis le bon comportement devrait être "spip détecte qu’il y a un version base plus récent, il refuse l’installation"

• Libav (ffmpeg) What is the most robust way to set the output stream time base ?

  29 octobre 2016, par Jason C

  This is a follow up to the solution to this question. My question is : When creating a new output stream, what is the most robust way to ensure that the output stream time base is set to a valid value for arbitrary formats ?

  Another way to phrase this question is : If I leave the output stream time base set to 0/0, will avformat_write_header always initialize it to something appropriate ?

  Consider the following snippet (assume, unlike the above linked question, that I’m just encoding video and I do not have any input video timing info to refer to or copy from) :

  AVFormatContext *formatx;
  
  AVCodec *codec;
  
  AVStream *stream;
  
  ...
  
  stream = avformat_new_stream(formatx, codec);
  
  stream->time_base = { 1, 10000 };
  
  ...
  
  avformat_write_header(formatx, NULL);

  Here, my rationale is as follows :

  • I observed, for MOV output formats, that if the stream time base is 0/0 when avformat_write_header is called, it is changed to 1/90000. Conclusion : At least one format (MOV) has a preferred time base that is set here, so others may be the same.
  • I do not know if avformat_write_header can be relied on to do this first, so I figure I’ll give it an initial reasonable value (1/10000) just in case.

  So this covers cases where avformat_write_header doesn’t set the time base. However, now I’ve observed two worrisome things :

  • If I do initialize the time base (to 1/10000 in this case), avformat_write_header does not modify it. No worries yet, except...
  • As an experiment I set it to 1/1000000. The MOV muxer issued a warning that the time base was too high. This means avformat_write_header seems to obey the time base that was set even if it’s not necessarily appropriate for the muxer.

  So my conflict is as follows :

  • If I don’t set the time base before writing the header, then I know that in at least some cases avformat_write_header will initialize it to something appropriate. However, I don’t know if this is true in all cases, so I run the risk of this failing (or do I ? that’s the question here).
  • If I do set the time base before writing the header, then I’m safe in situations where avformat_write_header doesn’t, but I run the risk of breaking the muxer, since I can’t know what time bases are valid for arbitrary muxers (or can I ?)
  • The time base can’t be changed after writing the header, of course. So I can’t initialize it to 0/0 then check it for validity and set it to something afterwards. That is, if I set it to 0/0, and avformat_write_header does not fill it in, then I’ve missed an opportunity to set it myself and the program unnecessarily fails.

  So what do I do ? How do I ensure that an output stream time base is both a) always set, and b) always set to something appropriate for the muxer ?

• build : change checkheaders to use regular build rules

  7 août 2012, par Mans Rullgard

  build : change checkheaders to use regular build rules