Audio Effect On Compressed Video

[xzerst]

I wanted to know when encoding a movie to 700 mb, would choosing original for the audio output type degrade the video as opposed to choosing mp3? I would prefer to output to original audio but was worried about affecting the video quality.

[manono]

Hello and welcome to the forum-

...would choosing original for the audio output type degrade the video as opposed to choosing mp3?

If the original audio is AC3 and you don't convert it to MP3, then in all cases it will degrade the video quality. Whether or not it's enough for you to notice will depend on the type of AC3 and the compressibility of the movie. For example, I'm making an AVI of a 2 hour movie for 1 CD at the moment. It compresses very well. It has 2 original AC3 streams. One is DD 5.1@384. Its size is 338 MB. The other AC3 is DD 2.0@192 with a size of 169 MB. The MP3 I made has a size of 118 MB. It saves 51 MB when compared to the DD 2.0 and a whopping 220 MB when compared to the DD 5.1. The video size alone is 576 MB (audio, subs, and overhead bring it up to 701 MB). Had I used the DD 2.0 AC3, the video quality would have been degraded by something like 9%. Maybe noticeable with the same resolution and settings, and maybe not. Had I used the DD 5.1, the video quality would have been degraded by somewhere around 40%. That would definitely have made the video look very bad at the same resolution and settings.

When going for 2 CDs, the effect is much less. The available space increases by 700 MB, the audio sizes stay constant, and the percentage effect on the video is much less. Ordinarily, if you want to use the AC3, it's a good idea to go for 2 CDs. There aren't too many movies that compress so well that you can use the AC3 in a 1 CD rip. When in doubt, run the Compression Test if using GKnot, or check the Compress Test results if using AutoGK.

[xzerst]

Okay, thanks for clearing that up.