[FFmpeg-trac] #3743(avcodec:open): mpeg2video decoder loses frames when progressive_sequence flag flips

FFmpeg trac at avcodec.org
Fri Jun 27 23:59:37 CEST 2014


#3743: mpeg2video decoder loses frames when progressive_sequence flag flips
-------------------------------------+-------------------------------------
             Reporter:  SianLiao     |                    Owner:
                 Type:  enhancement  |                   Status:  open
             Priority:  normal       |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  mpeg2video   |               Blocked By:
  regression                         |  Reproduced by developer:  1
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Changes (by michael):

 * priority:  important => normal
 * type:  defect => enhancement


Comment:

 the progressive sequence flag isnt allowed to change in mpeg, thus this is
 a bug in the used encoder.

 Where is this file from ?

 {{{
 mpeg2:
 In repeat sequence headers all of  the  data  elements  with  the
 permitted
 exception    of     those     defining     the     quantisation
 matrices
 (load_intra_quantiser_matrix,      load_non_intra_quantiser_matrix
 and
 optionally  intra_quantiser_matrix  and  non_intra_quantiser_matrix)
 shall
 have the same values as in  the  first  sequence  header.  The
 quantisation
 matrices may be redefined each time that a sequence  header  occurs  in
 the
 bitstream (Note  that  quantisation  matrices  may  also  be  updated
 using
 quant_matrix_extension()).
 All of the data elements in the sequence_extension() that follows  a
 repeat
 sequence_header()  shall  have   the   same   values   as   in   the
 first
 sequence_extension().
 If a sequence_scalable_extension() occurs after the first
 sequence_header()
 all    subsequent    sequence    headers    shall     be     followed
 by
 sequence_scalable_extension() in which all data elements are the same as
 in
 the    first    sequence_scalable_extension().
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/3743#comment:4>
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