[FFmpeg-user] DTS-HD copy same with or without dca_core

[Moritz Barsnick]

On Wed, Dec 05, 2018 at 00:11:53 +0100, Carl Eugen Hoyos wrote:
> 2018-12-04 23:24 GMT+01:00, sean darcy <seandarcy2 at gmail.com>:
> 
> > ffmpeg -i /opt/2T1/video/plex/Movies/Shows/WSS-Dance_t02.mkv -map v -map
> > 0:1 -bsf:a dca_core -c:a copy -c:v libx265 -crf 26 -preset slower -dn
> > -sn -nostdin /opt/2T1/video/plex/Movies/Shows/wss-dance-265.mp4
> 
> Please run "ffmpeg -i wss-dance-265.mp4"

In other words: You (sean) are trusting the info ffmpeg's muxer is
printing when creating the file. The actual output file, if you check
it afterwards, should be DCA Core. (I just tested the bitstream filter,
it seems to work just fine with the first DTS-HD MA 5.1 48 kHz sample
from here: https://thedigitaltheater.com/dts-trailers/)

I assume this is an issue with bitstream filters not modifying stream
property information, and thus the muxer not knowing about the change.
For video bitstreams, there is a thread / patchset on ffmpeg-devel
regarding exactly this:

http://ffmpeg.org/pipermail/ffmpeg-devel/2018-December/236990.html

(And I don't know how to change this in the dca_core bitstream filter,
though it shouldn't be difficult.)

In other words: Don't trust ffmpeg's printout when muxing, instead look
at the resulting file.

Moritz