Okay, I just recorded four samples from BBC HD (sadly, BBC One HD for two and BBC HD for two - I had to switch to get another Audio Described programme). I'll do some more testing later with Bruce Almighty, since it seems to be Hollywood fodder that shows the symptoms most regularly.
So: one programme on DVB-S2, mkv and ts containers; another programme on DVB-T2, mkv and ts containers.
Summary of this, though:
1. On satellite, the audio streams are clearly "soundtrack" and "the soundtrack with additional audio descriptions"
2. On terrestrial, they're clearly "the soundtrack" and "the audio description bit only" - no dialogue or background noises on the second track
If my suspicion on language is correct (i.e. there's something missing for the dialogue in a given language, even if only English is broadcast in the UK) then I need to find something more international than BBC drama, hence the search for something more blockbustery. Otherwise, it's all rolled into track 1, which is fine unless you're trying the AD stream.
Just for completeness (and to capture it), lightly-edited ffmpeg output:
MKV on DVB-S2:
Input #0, matroska,webm, from 'HD Test 1 - mkv on DVB-S2.mkv':
Metadata:
title : HD Test 1 - mkv
Duration: 00:09:29.44, start: 0.000000, bitrate: 6802 kb/s
Stream #0:0(eng): Video: h264 (High), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
Stream #0:1(nar): Audio: mp2, 48000 Hz, stereo, s16, 256 kb/s (default)
Stream #0:2(eng): Subtitle: none (default)
Stream #0:3(eng): Audio: ac3, 48000 Hz, stereo, s16, 192 kb/s (default)
Stream #0:4(eng): Subtitle: text (default)
TS on DVB-S2:
Input #0, mpegts, from 'HD Test 2 - ts on DVB-S2.ts':
Duration: 00:09:01.16, start: 1562.247600, bitrate: 8042 kb/s
Program 1
Stream #0:0[0x157c]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 26.30 fps, 25 tbr, 90k tbn, 50 tbc
Stream #0:1[0x157e](nar): Audio: mp2 ([4][0][0][0] / 0x0004), 48000 Hz, stereo, s16, 256 kb/s
Stream #0:2[0x1580](eng): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006)
Stream #0:3[0x157d](eng): Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, stereo, s16, 192 kb/s
No Program
Stream #0:4[0x157f]: Unknown: none
MKV on DVB-T2:
Input #0, matroska,webm, from 'HD Test 3 - mkv on DVB-T2.mkv':
Metadata:
title : HD Test 3 - mkv
Duration: 00:09:30.20, start: 0.000000, bitrate: 5383 kb/s
Stream #0:0(eng): Video: h264 (High), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 1k tbn, 50 tbc (default)
Stream #0:1(eng): Audio: aac, 48000 Hz, stereo, s16 (default)
Stream #0:2(eng): Audio: aac, 48000 Hz, stereo, s16 (default)
Stream #0:3(eng): Subtitle: none (default)
TS on DVB-T2:
Input #0, mpegts, from 'HD Test 4 - ts on DVB-T2.ts':
Duration: 00:08:59.52, start: 71939.750144, bitrate: 5675 kb/s
Program 1
Stream #0:0[0x19c9]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 28.94 fps, 25 tbr, 90k tbn, 50 tbc
Stream #0:1[0x19ca](eng): Audio: aac_latm ([17][0][0][0] / 0x0011), 48000 Hz, stereo, s16
Stream #0:2[0x19ce](eng): Audio: aac_latm ([17][0][0][0] / 0x0011), 48000 Hz, stereo, s16
Stream #0:3[0x19cd](eng): Subtitle: dvb_subtitle ([6][0][0][0] / 0x0006)
I'll try to get a few 5-minute samples of something later that I can share (otherwise, I'm uploading a 7Gb sample file somewhere to avoid damage by cutting...!).
I suppose it is perfectly possible that it's something peculiar to my DVB-T2 stick (a PCTV T2 nanostick 290e) if no-one else sees this... I'll have a think how to bypass tvheadend and see if anything else sees the same issue.
Can someone remind me why we all do this, rather than just buy a Sky+ box or similar? :)
