Recherche avancée

Sur d’autres sites (6579)

• avformat/matroskaenc : Ensure that ChapterUID are != 0

  26 novembre 2019, par Andreas Rheinhardt

  avformat/matroskaenc : Ensure that ChapterUID are != 0
  AVChapters have an int as id field and therefore this value can appear
  
  <= 0. When remuxing from Matroska, this value actually contains
  
  the lower 32 bits of the original ChapterUID (which can be 64 bits).
  In order to ensure that the ChapterUID is always > 0, they were offset
  
  as follows (since 07704c61) : First max(0, 1LL - chapter[i].id) was computed
  
  and stored in an uint32_t. And then the IDs were offset using this value.
  This has two downsides :
  
  1. It does not ensure that the UID is actually != 0 : Namely if there is
  
  a chapter with id == INT_MIN, then the offset will be 2^31 + 1 and a
  
  chapter with id == INT_MAX will become 2^31 - 1 + 2^31 + 1 = 2^32 = 0,
  
  because the actual calculation was performed in 32 bits.
  
  2. As soon as a chapter id appears to be negative, a nontrivial offset
  
  is used, so that not even a ChapterUID that only uses 32 bits is
  
  preserved.
  So change this by treating the id as an unsigned value internally and
  
  only offset (by 1) if an id vanishes. The actual offsetting then has to
  
  be performed in 64 bits in order to make sure that no UINT32_MAX wraps
  
  around.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• avformat/internal : Improve documentation of ff_packet_list_get

  19 août 2019, par Andreas Rheinhardt

  avformat/internal : Improve documentation of ff_packet_list_get
  The documentation of ff_packet_list_get currently didn't match the
  
  actual usage :
  
  1. It said that the destination packet is supposed to be initialized.
  
  But this makes no sense given that it will be overwritten completely and
  
  flacenc, mp3enc and ttaenc ignored this.
  
  2. ff_packet_list_get returns an int, although it can't fail in case the
  
  packet list is not empty (for which there is an assert). Again, several
  
  callers didn't check for any return value.
  
  In both cases, the documentation has been adapted to match actual usage.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavformat/internal.h

• If multiple channels, merge then take sample length from audio file and save it to s3

  18 mai 2017, par khinester

  I am using transloadit to extract the audio from a video file, which is then saved to S3.
  This works great, but I wanted to know how to :

  1. check if the file has multiple channels and then squash it inot one as per https://transloadit.com/demos/audio-encoding/merging-multiple-audio-streams/ - do I need to check for this or do i default to use this robot ?

  2. extract a small sample from the audio file - and save this as a separate file.

  For example, I have a 2h audio file from which I want to take 5% of the length and save this as sample.mp3

  In ffmpeg, i can cut :

  ffmpeg -ss 0 -t 30 -i original.mp3 sample.mp3

  but I am unsure how to chain this workflow, here is what i have thus far :

  const opts = {
  
    params: {
  
      notify_url: `${ process.env.SELF }/services/trans/${ jwToken }`,
  
      steps:      {
  
        import: {
  
          robot:  '/s3/import',
  
          use:    ':original',
  
          bucket: process.env.S3_INGEST,
  
          path:   ingest.key,
  
          key:    process.env.AWS_ID,
  
          secret: process.env.AWS_SECRET,
  
        },
  
        encode: {
  
          robot:        '/audio/encode',
  
          use:          'import',
  
          ffmpeg_stack: 'v2.2.3',
  
          preset:       'aac',
  
          ffmpeg:       {
  
            ab:  '128k',
  
          },
  
        },
  
        export: {
  
          robot:   '/s3/store',
  
          use:     'encode',
  
          bucket:  s3Export,
  
          path:    `${ prefix }/${ token }.m4a`,
  
          headers: {
  
            'Content-Type': 'audio/mp4',
  
            'x-amz-server-side-encryption': 'AES256',
  
          },
  
          key:    process.env.AWS_ID,
  
          secret: process.env.AWS_SECRET,
  
        },
  
      },
  
    },
  
  };

  in the docs, https://transloadit.com/docs/conversion-robots/ i can’t see how to do this ?

  any advice is much appreciated.