This is the sixth time I have attempted to send this to the list. I think Lou
may have identified the issue, so I am trying a different way of posting this
and hope it will go through. If it does, thanks Lou!
I have a strange situation in that I have a satellite receiver that receives
one particular channel that has a rather different audio arrangement. I can
record programs, but at the moment I can't play them back and hear the full
audio on my home theater PC.
The facts are:
The recordings are from a DVB-S2 satellite source and are saved as .ts files.
Each .ts file only contains the recording of a single channel; it's not one of
those .ts files that contains a raw dump from a transponder with many channels.
The video is fine as is and does not need to be converted, it's only the audio
that is a problem.
The recordings contain four different audio streams or tracks or channels (each
software program calls them something different; I will refer to them as
streams hereafter), each of which have a left and right channel.
Most software by default only plays the first stream, which contains only
background music and sound effects in stereo, but no dialogue. You can select
a different stream but no matter which you select, you wind up missing some of
the audio.
QuickTime on an OS X machine will play all the audio streams merged together
and normally that sounds pretty good, except when there is a "described video"
track (that narrates the action for sight-impaired users). Since at this point
in my life I don't have any vision problems that severe, I'd prefer not to hear
that track, but QuickTimes give you no way to selectively turn it off, and
anyway my HTPC box runs Ubuntu Linux, so running QuickTime there is not an
option. I really want to be able to play the recordings in XBMC.
As best I can tell, the way the broadcaster is sending the tracks appears to be
as follows:
Stream 1: Background Music and sound effects in stereo
Stream 2: Left channel is vocal audio and a few additional sound effects.
Right channel appears to be low-level background noise only.
Stream 3: Appears to be rear channel audio (but no dialogue) in stereo
Stream 4: Left channel is either blank or contains described video narration
(which I do NOT want). Right channel contains dialogue but sometimes with
slight reverb, probably for surround sound systems.
If my guess on that is accurate, and I am not 100% sure it is, then my
suspicion is that the way the channels are supposed to be mapped are as follows:
Stream 1: Front left and right speakers
Stream 2: Left channel (dialogue) to center speaker. Not sure about right
channel, maybe mixed with front center?
Stream 3: Rear left and right speakers
Stream 4: Left channel for described video or alternate language. Right channel
to rear center OR mixed with front center.
But, it would be acceptable to take the stream 2 Left channel and send it to
the front left speaker, and the stream 4 right channel and send it to the front
right center, mixed with the stream 1 audio of course. What is not wanted is
the stream 4 left channel audio. This is what I believe QuickTime is doing,
just mixing all the lefts together and all the rights together, and it sounds
pretty good except when that unwanted described video track is present.
I have found that I can use this to get rid of the unwanted left channel in
Stream 4:
ffmpeg -i "original_program.ts" -c:v copy -map 0:0 -map 0:1 -map_channel 0.1.0
-map_channel 0.1.1 -map 0:2 -map_channel 0.2.0 -map_channel 0.2.1 -map 0:3
-map_channel 0.3.0 -map_channel 0.3.1 -map 0:4 -map_channel -1 -map_channel
0.4.1 -c:a mp2 test.ts
That may not be the optimal way to do that (suggestions to streamline that
would be appreciated) but it took me over six hours to get that much figured
out. Unfortunately, it still saves the remaining audio as four separate streams:
Output #0, mpegts, to 'test.ts':
Metadata:
encoder : Lavf55.33.100
Stream #0:0: Video: h264 ([27][0][0][0] / 0x001B), yuvj420p, 1920x1080 [SAR
1:1 DAR 16:9], q=2-31, 29.97 fps, 90k tbn, 29.97 tbc
Stream #0:1(aaa,aab): Audio: mp2, 48000 Hz, stereo, s16, 128 kb/s
Stream #0:2(aac,aad): Audio: mp2, 48000 Hz, stereo, s16, 128 kb/s
Stream #0:3(aae,aaf): Audio: mp2, 48000 Hz, stereo, s16, 128 kb/s
Stream #0:4(aag,aah): Audio: mp2, 48000 Hz, stereo, s16, 128 kb/s
Stream mapping:
Stream #0:0 -> #0:0 (copy)
Stream #0:1 -> #0:1 (mp2 -> mp2)
Stream #0:2 -> #0:2 (mp2 -> mp2)
Stream #0:3 -> #0:3 (mp2 -> mp2)
Stream #0:4 -> #0:4 (mp2 -> mp2)
This does not help me at all in XBMC. What I need to figure out is how to
combine all the streams and merge them down to a single stereo stream (5.1
would be better, but at this point even plain stereo would be a huge
improvement). Does ffmpeg have this capability?
TVHeadEnd will let you post-process a recording automatically as soon as the
recording ends, so I was thinking that if it were possible to do this with
ffmpeg, maybe I could run it that way. Problem is, prior to looking at it for
this use, I have have no experience at all with ffmpeg (other than being
vaguely aware that it's a prerequisite for certain other software packages) so
I have no idea what it's capable of, nor what options I would need to use to
get the result I want.
_______________________________________________
ffmpeg-user mailing list
[email protected]
http://ffmpeg.org/mailman/listinfo/ffmpeg-user
