bbmpeg....message, mux rate may be to low for data rate...ho

[CarterZ]

Adam, can you be a bit more specific about the mux rate?

i presume that it controls how many bytes of data are inserted for the video and audio at any given point.... but the details are a bit foggy....

thanks
CZ

[adam]

The mux rate directly corresponds to the datarate (bitrate.)

Basically its the rate at which the data will be read from the mpg. I really dont know enough about it to give a detailed description. bbmpeg has the muxrate automatically set according to the standard. If your bitrate did not exceed the maximum of 2,788,800 bits/sec than you would be fine. But programs like TMPGenc simply are not built %100 according to spec so you will rarely make a totally svcd compliant mpeg2, but like I said the non-compliant peaks are so minor that they usually dont hurt.

Setting the mux rate to 0 in bbmpeg lets it choose the mux rate for you, so even if your datarate is non-compliant it will still be ok, assuming your hardware player can handle it.

[AE-35]

I think it is a problem, atleast for my Pioneer 535.
When I get peaks over the specified SVCD rate in my MPEG file the audio is out of sync after 20 minutes, when I press pause and play it's fine again.
This doesn't happen when I encode at a lower bitrate.
Is there any encoder that respects the max bitrate I tell it to encode at ?

[stanwebber]

6972 is the maxmimum svcd mux rate where 6972 is in 50 byte/sec units, so the maximum combined video/audio mux rate in bps is 2788800 (6972x50x8). each sector is 2324 bytes and at a mux rate of 348600 bytes/sec (6972x50), 150 (348600/2324) sectors/second are read. out of the 2324 bytes of a sector a minimum of 22 bytes (pack header+PES header) are needed for muxing overhead. so the minimum muxing overhead is 26400 bps (22x8x150). svcd also specifies that the sequence headers start at the beginning of a PES packet. what this means is that if a sequence header was going to fall into the middle of a sector, the bytes remaining in the sector should be filled with a padding packet and the sequence header would then be placed at the beginning of the PES packet in the next sector. the unused bytes in this sector (now a padding packet) are wasted but they still count in the total bitrate. in a 15/3 GOP structure at 29.97fps there are 2 sequence headers every second, so assume the case where a 1/2 of the bytes of two sectors are wasted, this yields 18592 bps additional muxing overhead. 2788800 - 26400 - 18592 = 2743808bps maximum combined video/audio bitrate to avoid pts/dts muxing errors assuming your encoder is accurate enough. remember to calculate bitrates correctly i.e. 2600 video is 2662400bps (2600x1024), 128 audio is 131072bps

<font size=-1>[ This Message was edited by: stanwebber on 2001-07-11 01:47:31 ]</font>