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DV50 MXF 1A

Developers
guhlda
2011-09-15
2013-04-25
  • guhlda
    guhlda
    2011-09-15

    Hello,

    Most Material Resolutions are discrete files (MXF ATOM). There are very few common ones (DVD/.PS, MOV or MXF OP1A).

    I need a material resolution suited for live and low latency. MPEG/DVD has too high latency, MOV can not be read untill the file is completed (important trailer needed by player).

    I would like to implement DV25/50/100 MXF OP1A. Is there something I should know before starting ?

    Guhlda

     
  • Philip de Nier
    Philip de Nier
    2011-09-16

    Not really. You need to do something similar to the D10 writer in the database, recorder and MXF writing parts of the code. You'll probably need to modify MXFOP1AWriter to be an abstract class with a D10 and (more generic) OP1A writer as sub-classes.

    Philip

     
  • guhlda
    guhlda
    2011-09-20

    Well finally I will use IMX30 MXF 1A, that will give functionality I need (intraframe compression mostly).

    Now I have noticed various differences when playing such a file with player -mxf or player -ffmpeg:

      1. timecodes: -mxf reports proper recorded frames timecodes, while -ffmpeg always starts from 0:0:0:0. -ffmpeg reports the proper recording timestamps from an MPEG .ts file.
      2. growing file (if the file is played while being recorded): using -ffmpeg is fine, while using -mxf I get an error about the missing mxf header, and player stops.

    Of course I need both features, proper recording timecodes and ability to read an mxf while being recorded. Is it possible to tweak the recorder to update the header at file creation ? Or would it be easier to act on -ffmpeg ?

    Can you give me some advice ?
    Thank you
    Guhlda

     
  • Philip de Nier
    Philip de Nier
    2011-09-21

    1. the timecode information is stored in the MXF metadata. FFmpeg doesn't extract that information and that's why the player defaults to 0:0:0:0. FFmpeg does extract timecode information from an MPEG transport stream file.

    2. See my response in the "player -ffmpeg from a growing file" topic

    I suggest you try the -mxf option.

    Philip