[FFmpeg-trac] #4354(undetermined:new): Big file size difference after using -c:v copy and -c:a copy

FFmpeg trac at avcodec.org
Sun Mar 29 01:37:08 CET 2015

#4354: Big file size difference after using -c:v copy and -c:a copy
             Reporter:  Atarikid  |                    Owner:
                 Type:  defect    |                   Status:  new
             Priority:  normal    |                Component:  undetermined
              Version:  2.5.2     |               Resolution:
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |

Comment (by AndyF):

 Replying to [ticket:4354 Atarikid]:
 > I noticed some very strange when copying streams.
 > You can reproduce this with any .m2t or .ts source file.
 > Just copy the streams with -c:v copy -c:a copy
 > Note the below example source file has 1 video stream and 1 audio
 > Do notice the BITRATE has changed from 27253 kb/s to 19490 kb/s
 > How can this be the case when you copy the streams?

 Transport streams may contain null packets to pad out bandwidth to a fixed
 value which could account for it.

 I've never used one, but search for transport stream analyzer and I guess
 you will be able to find something to look at your streams. Null packets
 have pid 0x1fff (8191).

Ticket URL: <https://trac.ffmpeg.org/ticket/4354#comment:3>
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