[mythtv-users] SD DVB-T in the UK: Surround Sound?

[John Pilkington]

On 14/01/11 12:17, Paul Gardiner wrote:
> On 14/01/2011 12:06, Alex Butcher wrote:
>> On Fri, 14 Jan 2011, Paul Gardiner wrote:
>>
>>> On 14/01/2011 10:33, John Pilkington wrote:
>>>> My recording of the first episode of the new series "Human Planet" from
>>>> BBC1 (SD DVB-T) is marked as being in "Surround Sound". I don't think
>>>> I've seen this before. I've now deleted the original recording but
>>>> ffmpeg -i looks as usual:
>>>>
>>>> Stream #0.0[0x258]: Video: mpeg2video, yuv420p, 720x576 [PAR 64:45 DAR
>>>> 16:9], 15000 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
>>>> Stream #0.1[0x259](eng): Audio: mp2, 48000 Hz, 2 channels, s16, 256
>>>> kb/s
>>>> Stream #0.2[0x25a](eng): Audio: mp2, 48000 Hz, 1 channels, s16, 64 kb/s
>>>> Stream #0.3[0x25d](eng): Subtitle: dvbsub
>>>> Stream #0.4[0x261]: Data: [5][0][0][0] / 0x0005
>>>>
>>>> Is this a real New Thing or just a mistake in the flags?
>>>
>>
>> We're talking about the 256kbps stereo stream and the 64kbps mono
>> streams,
>> right? I think I see these a lot. This is why I added logic to pick the
>> 'best' (um, biggest!) audio stream to mythburn.py.
>>
>>> Might it be flagging the use of pro logic?
>>
>> Or a Welsh soundtrack? Or a descriptive narration for the
>> visually-impaired?
>
> No, I mean marking it as "Surround Sound" may just mean the main
> stereo stream encodes a pro-logic back channel. BBC have been
> using pro-logic for ages.
>
> Paul.

I don't think the 64kb/s channel has anything to do with this:  it's 
just the usual 'audio for the visually impaired' track and may or may 
not be always active; but is the main stereo channel now including new 
info that could be accessed, and am I throwing that away by treating 
'Stream #0.1' as pure stereo - remembering that this is an SD 
transmission?  Might 're-encoding to ac3' (which is the default in 
MythArchive) actually recover something or is it just there because 
equipment for the American market doesn't understand mp2?

John P