XRECODE

Direct encoding any multichannel source (*.pcm, *.dts) to stereo/joint stereo *.mp3 results in increasing playback speed. Looks like three times faster in case of 5.1 channels to stereo. Older versions and the current one.

I cannot reproduce the issue. Are you using the latest (1.104) version from https://xrecode.com?
If so, please send the Diagnostic information (it's under About button) to xrecode@gmail.com
It would be nice if you could share the source multi-channel file as well (via https://wetransfer.com/ or other service) to xrecode@gmail.com.

Required information has been sent.

Here's the update to try https://xrecode.com/test2/setup_xrecode ... _1.105.exe

So far encoding from *.dts and *.wav shows correct playback speed. Tomorrow I'll try with 4.0 and 5.0 tracks and report results.

It looks fine with other input files, but... Please, check the duration of input and output files. I can't estimate the difference by ear, but MediaInfo gives different values for input and output files, see picture.

I don't really know. When you convert that mp3 to wav, you will get exactly 20 s 00 ms duration.

Maybe that's correct for backward encoding. But I tried one more file PCM 96KHz-24bit-5.1 → MP3 48KHz-8bit-2.0 (joint stereo) to encode. The result is the same - different duration (see picture). The difference is hundredths of a second, but still. It might be audible for piano recordings and visible for the whole album/concert.

I don't know what exactly is going on here, but I converted that 5.1 wav file to wav 2.0 (duration in Mediainfo 20:00) and then manually converted it to 320/CBR mp3 via lame.exe and duration shown by MediaInfo was also 20:40.

I don't know also.
One more attempt today: DTS HD Master Audio file 96-24-5.0 (duration 01min 18,190) direct convert to mp3 320 CBR joint stereo gives output file with duration 01 min 18,960.