mplex details; 'mux as...' settings

[hirshfield]

Hi all,

Firstly wishing a very merry Christmas and happy New Year to all readers . Thanks Major for the new release (and subsequent few patches!). Wow, support over the holidays, fabulous!

Just a small pick at your brains this time, being the guru that you are - for my own peace-of-mind.

What are the variables used by the 'mplex' tool doing to my mpeg, in addition to muxing them of course?

I don't want to include entire console logs just for the sake of this question, so instead I hope it's enough just to give an overview:

I'm multiplexing a VBR 2000Kbps 352x480 mpeg2 video with 224/44100 mp2 audio successfully encoded from a DivX (as per my last enormous post!)

You're using mplex 2.2.2(2003/05/13) binary in ffmpegX. I have used this and for experimentation the version included in "rnc's Missing Tools - MMT-EZ" which is mplex 2.2.1(2002/04/20). They're both 1.7.0 although yours is mpex-2 if that means anything.

On using these two versions of mplex I receive differing figures for the following variables, although the final mpeg file sizes are identical. I have stated below the SVCD and XSVCD figures using ffmpegX with the included mplex and MMT-EZ's SVCD setting using there included mplex. If I swap the mplex versions between tools, the returned values are mplex specific for SVCD settings.

==========

INFO: [mplex] rough-guess multiplexed stream data rate:
SVCD-2873048 XSVCD-2873048 MMT-2881600
INFO: [mplex] target data-rate specified
SVCD-2873048 XSVCD-3000000 MMT-2788800

SVCD- INFO: [mplex] Run-in Sectors = 78 Video delay = 46800 Audio delay = 50553
XSVCD- INFO: [mplex] Run-in Sectors = 78 Video delay = 43505 Audio delay = 47259
MMT- INFO: [mplex] Sectors = 78 Video delay = 46800 Audio delay = 46800

INFO: [mplex] STREAM e0 completed @ frame
SVCD-183319 XSVCD-183319 MMT-183319
INFO: [mplex] STREAM c0 completed @ frame
SVCD-292696 XSVCD-292696 MMT-292697

(ffMpegX only ++ WARN: [mplex] Discarding incomplete final frame MPEG audio stream c0! - this explains the above difference!)

INFO: [mplex] Multiplex completion at SCR=
SVCD-688179000 XSVCD-688176000 MMT-688175400

SVCD- INFO: [mplex] Video e0: buf= 234896 frame=183319 sector=00836113
SVCD- INFO: [mplex] Audio c0: buf= 1901 frame=292696 sector=00093244
XSVCD- INFO: [mplex] Video e0: buf= 234896 frame=183319 sector=00836113
XSVCD- INFO: [mplex] Audio c0: buf= 1901 frame=292696 sector=00093244
MMT- INFO: [mplex] Video e0: buf= 234122 frame=183319 sector=00836113
MMT- INFO: [mplex] Audio c0: buf= 1170 frame=292697 sector=00093244

INFO: [mplex] Video Stream length:
SVCD-1908557291 XSVCD-1908557291 MMT-238569583
INFO: [mplex] Audio stream length
SVCD-214086953 XSVCD-214086953 MMT-214087680


The following returned values are all constant between trials:
INFO: [mplex] Sequence headers: 12222
INFO: [mplex] Sequence ends : 1
INFO: [mplex] No. Pictures : 183319
INFO: [mplex] No. Groups : 12222
INFO: [mplex] No. I Frames : 12222 avg. size 26228 bytes
INFO: [mplex] No. P Frames : 48886 avg. size 15435 bytes
INFO: [mplex] No. B Frames : 122212 avg. size 6819 bytes
INFO: [mplex] Average bit-rate : 1996800 bits/sec
INFO: [mplex] Peak bit-rate : 3330800 bits/sec
INFO: [mplex] BUFFERING min 15 Buf max 223000

INFO: [mplex] Syncwords : 292698
INFO: [mplex] Frames : 167256 padded
INFO: [mplex] Frames : 125442 unpadded
INFO: [mplex] BUFFERING min 16 Buf max 746
INFO: [mplex] MUX STATUS: no under-runs detected.

==========

Please could you explain the effect of the muxed bitrate, run-in sectors, and especially this delay setting, as the video/audio delays are equal in the MMT-EZ mplex and ffmpegX's mpeg2 mux setting. Are they having any effect on the final mpeg sync?

I understand if you are unable to offer any assistance regarding the mplex included in rnc's tool, however even without this example included, the figures and delay's are significantly different between ffmpegX's own "mux as..." options.

Mpeginfo tool reports different muxed bitrate between SVCD and XSVCD even with the same source elementary streams. The XSVCD says 3.0 Mbps while SVCD is 2.79 Mbps. Running time's also differ slightly. How can this occur and what would be final SVCD effects on playback/compatibility/etc, when all file sizes are identical?

Thanks again and again for all your help and expertise.
Wishing you well over the holidays,

Adam Hirshfield

[major]

mplex is run in auto-detection mode (with profiling), so it decides itself what to do with the streams and all the parameters you see in the output are self-detected.

It seems to me normal that old versions of mplex behave slightly different than newer ones. The max bitrate is a ceiling value used sometimes when mplex is unable to find it himself.

The profile adds some specific muxing features like NAV packets for DVD, etc. Also XSVCD/XVCD should only be used when the encoding settings are not strictly SVCD/VCD compliant (and the opposite for SVCD/VCD).

If you experience sound sync issues which seem to be originated by the muxing step itself, please provide applicable clips and examples. Most often, sync issues are originated during video encoding as a consequence of an incorrect framerate.