opposite problem with mono wav -> ac3

[OogaBooga]

i'm getting the opposite of the problem other people had with encoding a mono wav file to ac3. i originally captured video at 44100hz/16bit/mono because my source was mono vhs and i wanted to make svcd. i then decided to try making a dvd so i used procoder to upsample to 48000hz/16bit/mono. the length of the wav file is 5:05. if i encode this wav to mp2 then i still get the correct output length of 5:05, but if i encode to ac3 then my file becomes 10:11 with the sounds playing at half speed. i thought my problem was the same as other people's so i used the mono-to-stereo plugin. this gave me a 20:22 file instead that played at quarter speed. i am using besweet 1.5b18 with besweetgui 0.6b76. i tried using besweet 1.4 but that just crashes as soon as i press the wav->ac3 button. gui 0.6b61 with besweet 1.4 gave me the same crash, while using 1.5b18 gave the same half speed ac3.

has anyone else worked out how to encode a mono wav->ac3?

BeSweet v1.5b18 by DSPguru.
--------------------------
Using AC3enc.dll v0.2 by Gerard Lantau & Dg (http://ffmpeg.org).

Logging start : 06/16/03 , 15:52:35.

C:\Program Files\BeSweet\BeSweet.exe -core( -input h:\MPEG2_DVD_NTSC.wav -output h:\MPEG2_DVD_NTSC.ac3 -logfile C:\Program Files\BeSweet\BeSweet.log ) -ota( -G 0.95 -fs 48000 ) -ac3enc( -b 384 )

[00:00:00:000] +------- BeSweet -----
[00:00:00:000] | Input : h:\MPEG2_DVD_NTSC.wav
[00:00:00:000] | Output: h:\MPEG2_DVD_NTSC.ac3
[00:00:00:000] | Floating-Point Process: No
[00:00:00:000] | PostGain normalize to : 0.95
[00:00:00:000] | Source Sample-Rate: 48.0KHz
[00:00:00:000] +------- AC3ENC ------
[00:00:00:000] | Bitrate method : CBR
[00:00:00:000] | AC3 bitrate : 384
[00:00:00:000] | Channels Mode : 5.1
[00:00:00:000] | Error Protection: Yes
[00:00:00:000] +---------------------
[00:05:05:740] Conversion Completed !
[00:05:05:740] Actual Avg. Bitrate : 767kbps
[00:00:16:000] <-- Transcoding Duration

Logging ends : 06/16/03 , 15:52:51.

[Awatef]

1) be sure to encode to Dolby 1.0

2) The bitrate you choosed is way too high, go for something between 96k and 128k.

3) If you still get wrong length, convert the mono file you have to stereo with another application than BeSweet, WaveLab or CoolEdit for example. Then encode to Dolby 2.0
Recommended bitrate: between 192k and 256k

[OogaBooga]

converting the wav file to stereo first allowed the file to be encoded to ac3 properly. i don't think it's not a good solution though because i only have a mono source file so i don't see any point in creating a stereo final output.

the high bitrate was used originally because after i choose the bitrate in the besweet gui "ac3 & ogg" dialog, it automatically switches back to 384k if i make any changes on the "besweet" dialog.

[Awatef]

Well, it's fake stereo of course, but many people like that better because it gives you more spatial sound as it will be sent to the 2 front speakers L(eft) & R(ight) ... it kinda makes the front stage full.

If you encode in Dolby 1.0, only the C(enter) speaker will be working, which won't sound spatial, unless you tell your decoder that you have only 2 front speakers, so you gotta change it every time manually, as you may want to enjoy your 5.1 DVDs in full 5.1 richness ;)

[OogaBooga]

oops. i meant that i didn't think converting to stereo was a good solution, but i see your point about having a dual mono soundtrack. the weird thing is that if i convert double the frame rate then i get a double speed output as expected, but if i choose to adjust the frame rate from 29970 to 29970 (i.e. no change) i still get a half speed output.

[vmesquita]

Same problem here. Trying to encode a 48 khz mono track at 96 kbps. BeSweet 1.4 crashes, Besweet Beta 1.5 doesn't crash but gives me a low pitch sound... Also tried Soft Encode and this one gives me silence. I've been encoding in MP2, but I know this is not the best idea for DVD compatibility, I really wanted to use AC3. Is there any other software/setting to try ?

Since I am doing some low bitrate conversion from bad VHS sources ( 352x240 around 1400 kbps), going to Stereo makes a big difference in video bitrate, so I can't use this solution.

[]'s
Vmesquita

[Awatef]

big difference in video bitrate?! you kidding? only 96k difference between 96k and 192k! the difference will be unnoticeable!

You remember me of guys that do VCDs with 1246k & 128k instead of the standard 1150 & 224k. They say, it is to get better video quality, yeah right!.. 96k go unnoticed in the video part, but are vital for audio quality...

[vmesquita]

So difference between 1300 kps and 1400 is barely noticeable? I never tested, but I might try now that you said it. But still 96 kps mono would be better, since the source is mono anyway.

[]'s
Vmesquita