Divx to DVD with 5.1 AC3

[ashsharma]

I've got a Divx film with 6 channel AC3 audio and I want to convert this to Mpeg 2 and burn to DVD. Now usually I would demux the audio and encode the video using tmpgenc. But will this be ok for 5.1 audio as I would like to preserve the 5.1 rather than getting 2 channels.

On another note, when I load the divx into Gspot it tells me I don't have the correct video codec, however if I load it into avicodec it says that I already have a compatible codec. Which one should I trust and does it actually matter if I'm just encoding?

[DiablosuX102]

not sure i understand ur first question, but demux the 5.1 with virtualdubmod, vonvert the video to mpeg2 and then mux back in the audio...

[ashsharma]

I just want to make sure that if I demux the audio then mux after encoding that the audio will remain in 5.1 (as I'm typing out this question it sounds stupid-of course it'll remain 5.1)

Doesn't tmpgenc plus now support ac3 encoding?

[ashsharma]

I've tried encoding the divx film by first extracting the ac3 audio and it's worked fine...

However the outputted Mpeg was much larger than I expected. I used the bitrate calculator and worked out that my 1 hour 59min 45 sec film with audio at 384k should give me an average bitrate of 4700. Which I've used in tmpgenc. However this has produced an mpeg of about 6.5gb. I'm not sure what I'm doing wrong, I used the 2-pass vbr.

[ashsharma]

I am adding subtitles at the same time as encoding but this surely wouldn't add an extra 2gb? or is it a bad idea to use subtitles at the same time as the 2-pass vbr??

[mats.hogberg]

If you set the average bit rate for a 2 pass VBR encoding at 4700, you should get the file size you predicted. (You should lower it a bit, say to 4650 for some margin.)
It's not clear how you add the subtitles, but I take it you add permanent subs to the move. That shouldn't affect the file size.

/Mats

[ashsharma]

Yeah the subtitles are .sub files which I think is working ok. However I'm still have the problem with the output size.

Is it possible that when I'm analysing the divx with gspot it's giving me incorrect info? I say this because it tells me I don't have the correct codecs installed even after I've downloaded and installed them.

Also, the divx is split into 2 files, I've just added the 2 runtimes together to calculate the average bitrate, I assume this is correct? I suspect there is something wrong with the 1st divx file as is supposed to be 1hour long but takes twice as long to encode as usual(and 2x the 2nd divx file) it also produces the extra 2gb in the mpeg.

So it could be possible that the 1st divx is 2 hours and gspot is wrong?

[mats.hogberg]

Load them up in VirtualDub. Scan for bad frames. The source codec (or bit rate) doesn't affect destination file size - only source movie length*destination bit rate does.

/Mats

[ashsharma]

ok, thanks. I've used virtualdub before for extracting audio, but how do I scan for bad frames?

[mats.hogberg]

but how do I scan for bad frames?

Here and here.

/Mats

[ashsharma]

OK thanks I'll try that later.

Would bad frames be the cause of:

1. Tmpgenc taking twice as long to encode
2. Tmpgenc producing an mpeg twice as large as expected
3. Virtualdub mod taking twice as long to demux ac3 audio as expected?

All of the above have happened when I've tried to convert this divx.

[ashsharma]

but how do I scan for bad frames?

Here and here.

/Mats

can you use VDub-MP3 for ac3 audio though?

[DiablosuX102]

OK thanks I'll try that later.

Would bad frames be the cause of:

1. Tmpgenc taking twice as long to encode
2. Tmpgenc producing an mpeg twice as large as expected

try mainconcept, i just started using it, works great, should be around twice as fast.

[ashsharma]

It's not really the time tmpgenc takes in general, it's the fact that it tkaes taking twice as long ofr the 1st half of a movie and creating an mpeg twice as large as it should be.

[ashsharma]

There's no bad video frames but this is still driving me mad!

You do the maths:

1hr 59min 45s divx.

Got 6 channel audio at 384kbits/s

Gives a average bitrate of 4700 to fit onto a dvd.

But when I do this with tmpgenc it makes a mpeg that is 5.7Mb even before I muxed the audio! How is this possible?

Please help.

[mats.hogberg]

The AVI is corrupt somehow. Can't see any other explanation. Drag it over to the trash can and get on...

/Mats

[ashsharma]

Haha, When I start something I can't give up.

I've now got an idea of the problem.

it seems that because I was encoding 2 divx files using batch encode with the divx files being in the same folder and similarly named that tmpgenc was for some reason encoding both files and adding them to create one ~4gb mpeg then encoding the 2nd divx file to create a mpeg ~2gb. I'm not sure why this is.

So it appears it has worked, however if I load the 1st mpeg into tmpgenc, it says it 4.3Gb which is fine, however when I create the dvd files and open these in Nero to burn it says that the total size is only 2.3gb!

Aaaah!

[mats.hogberg]

One thing struck me - how are you encoding? To m2v (elementary video)or mpg (system a+v)? 2 unexplained additional GB for a 2 hr movie matches a LPCM sound track pretty close....!?!

/Mats

[ashsharma]

I'm encoding to m2v (elementary video).

I'm fairly sure the problem was tmpgenc encoding both divx and adding them together to 1 mpeg. I think I read somewhere on the forum about it doing this.

When I load the 1st divx in Tmpgenc and use the wizard on the last screen it tells me the output will be 119mins even though the source is 62mins! And when I scan through using the source range it had the entire movie even it's only supposed to be encoding the first divx! So even though it's doing it worng it still works.

When I open the 1st mpeg in tmpgenc dvd author, it gives me the impression that I have the whole movie and even allows me to set chapter points throughout the entire film. However once it's authored and burned to dvd it is clearly on the 1st half of the movie! Weird no?

So what I've now done is add the 1st 4.2gb mpeg and the first ac3 to tmpgenc dvd author then added the 2nd 2Gb mpeg and the 2nd ac3 to the same track and authored as normal, even though it tells me it'll be ~6.2gb and over the normal dvd size.

Then amazingly when I go to burn the vobs in Nero they total a mere 4.3Gb and burn perfectly.

So the movie plays fine now but I'm still not sure what went wrong!