Does TDA 1.6 shrink audio ?

[StoneColdWhat]

Alright so I noticed that in 1.6, when I started the process my file was 4300mb, when I go to burn it its 3800. I go thru the files and see if anything is cut, and nothing is so I was thinking maybe in TDA 1.6 in shrinks the audio ? I never had this happen when I used 1.5. My source is PCM no compression.

[guns1inger]

TDA will only shink audio if you tell it to. It can only encode to AC3 if you have the additional plugin, however it can probably do mp2. The easiest way to check is to open on of the resulting VOB files in g-spot 2.52beta and have a look.

[StoneColdWhat]

Yeah mine encodes to ac3 from the original pcm form, so is ac3 smaller then ? Hey speaking of which, not every1 has the ac3 plugin right ? Well a LONG time ago when I didn't use it I realized that the files would be outta sing. So TDA does make files smaller by going to ac3 then ? How come 1.5 didn't do this for me ? I had the option enabled in that, if it is infact shrinking the auto and not cutting out parts of the file, then it is useful because it saved about 500mb or so.

[guns1inger]

PCM audio has a bitrate of 1536 kbps, whereas AC3 is usually encoded as low as 192 kbps for 2 channels, through to 448 kbps for 5.1 (although TDA can only do 2 channel encoding). So the size difference can be drastic. This is something you should take into account when encoding your video, as you could have increased the video bitrate to make use of the extra space.

As to why 1.5 didn't do it for you, all I can think of is it wasn't configured properly.

[StoneColdWhat]

Hmm well my source is rmvb so I use EO-VIDEO 1.6 to extra the audio, someone told me to extract the audio as PCM - No Compression so I did that... so since its encoding to ac3 anyways I should probably extract it as that in the program right ? Speaking of ac3, doesnt' ac3 sound more quiet then regular audio formars ? atlease in some .avi's with ac3 anyways *cough*

[StoneColdWhat]

oh yeah this seems to be only happening with mpg1, I use the exact same source for mpg 2 and its not doing it.

[StoneColdWhat]

Any idea why its only doing it for mpg1 and not 2 ??

[guns1inger]

Some poeple believe it is lower. Generally it is because it has a wider dynamic range, so quiet parts are relatively quieter than the loud parts. cf TV, where there is little difference between the two extremes.

I have a reasonable AV amplifier, so I really don't notice if the audio is a little quieter - I just turn up an extra notch.

[SingSing]

Yes, it can, and it is often a useful feature.

Home video and Documentory DVD often has LPCM sound track ( uncompressed wave sound track ). TDA let you have the option to encode the audio to the compressed MP2. This let us get another ~10% of minutes on the DVDR, without reduction in video quality.

[StoneColdWhat]

Hmm you know I've got these 2 files, same source and audio, the sizes when I encoding them were the same but when I re-ripped them in TDA after I forgot to put some other files on the dvd, the sizes were different! Why is this ? I checked and there were no cut off parts.

[SingSing]

Demux the before and after vob/mpeg files to video and audio, to determine what really happened.

[StoneColdWhat]

Ok so the pic on the left is AFTER I ripped the files back after authoring it. The one on the left is straight outta tmpgenc.

I cut off the right side of the pic caz everything else is the same.

[SingSing]

According to the picture, you are re-encoding a DVD video into VCD video. The size will shrink because VCD is lower resolution than DVD.

TDA is known to predict the final file size incorrectly. If it predicts the outcome is 4300 MB, the outcome almost always smaller.

[StoneColdWhat]

Hmmm I'm not sure about the re-encoding DVD into VCD part, because once you author a dvd, doesn't the VCD data turn into MPG2 ? So when I re-rip it again it should be ripping as MPG2 ? Correct me if I'm wrong, but even if what you say is true, why is it that when I re-rip 2 files from the authored dvd, that they're the same length and yet different in size by about 60 mb ?

[SingSing]

Okay, got you, right is before and left is after.

1. Your VCD audio got upsampled to 48KHz, and encoded into 2ch AC3, which is smaller.

2. The TDA is predicting the outcome bigger than it really is, as usual.

Both of them make the output smaller than what TDA thinks. After a while you know how to predict the % yourself. To burn as much as you want on a DVD, just figure out the real MB yourself, and tell TDA to do it anyway when the TDA "too much" warning come out.

Good luck, and have fun.

[guns1inger]

Actually, the AC3 and mpeg1-layer2 audio will be the same size - they are both 224kbps. TDA won't have re-encoded the video at all, it will accept VCD mpeg1 video.

[StoneColdWhat]

Well i've always known that TDA was off in predicting the outcome size, but what I'm still not getting is why the 2 files which are the same length + same audio codec comes out in different size AFTER I RIP IT BACK from an already AUTHORED dvd. These files were the same size BEFORE I authored them.