[FFmpeg-trac] #3714(avformat:open): Remuxing mpegts results in 5% bigger file size than original file

FFmpeg trac at avcodec.org
Tue Jul 15 14:00:45 CEST 2014


#3714: Remuxing mpegts results in 5% bigger file size than original file
------------------------------------+------------------------------------
             Reporter:  DavJames    |                    Owner:
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  avformat
              Version:  git-master  |               Resolution:
             Keywords:  mpegts      |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  0           |
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Comment (by AndyF):

 You may find that the software that recorded the sample has heavily
 reduced the PAT/PMT packets.

 They do seem a lot lower than recordings I have and ISTR the recorder I
 use reduced them in the past, possibly a bit now, but not by as much, if
 at all, due to issues that arose from heavy reduction.

 There are slight differences between the sample and the remux in the vid
 and audio streams, but most of the extra size is more PAT/PMT packets and
 it seems that one is duplicated with a different PID - I don't know if
 that is intentional for eg. compatibility, or is an issue.

 Below is some output from a (rubbish) ts analyser I cobbled together ages
 ago. Apart from the dup the output from ffmpeg looks more like what I am
 user to seeing than the sample.

 {{{
 Sample -

 Total packets = 1585830   Errored packets = 0

    PID      Total      RAI     PUSI      PCR   PMD(ms)   CFail    Cut1
 Cut2   Flags

 0x0000       1384        0     1384        0        0       0        0
 0
 0x0100       1384        0     1384        0        0       0        0
 0
 0x0201    1555747        6     3660     3653       56       0   481150
 642662  AE PD EP DI
 0x0202      27314        1     6863        2        0       0   571861
 0  AE PD EP DI
 0x1fff          1        0        0        0        0       0        0
 0

 remux -

 Total packets = 1668255   Errored packets = 0

    PID      Total      RAI     PUSI      PCR   PMD(ms)   CFail    Cut1
 Cut2   Flags

 0x0000      39671        0    39671        0        0       0        0
 0
 0x0011       7906        0     7906        0        0       0        0
 0
 0x0100    1557595      325     7320     3688       40       0        3
 6095  AE PD EP DI
 0x0101      23412     1706     1697       13        0       0     4877
 4889  AE PD EP DI
 0x1000      39671        0    39671        0        0       0        0
 0

 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/3714#comment:5>
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