AC3 to AAC

[Carpo]

I don't know if i should stick with AC3 or go with AAC, my goal is to keep as much audio quality as i can while making a smaller audio file so i can give more quality to the video.

I have read the FAQ on AAC and i am still a little confused, could someone give me some options on which options to select? Do i go with HE-AAC or LC-AAC do i go with 64kbps or 128kbps?

At the moment i am mainly doing my old dvd collection of comedy series from the mid 90's so they will only have 2 channels, whereas some of the newer ones will be 5.1.

Another thing i am considering is if i should use AAC for my bluray backups or stick with the HD audio or down converting it, if i go with the latter what options would be advisable there?

[nurbs]

You choose HE or LC depending on the bitrate, or better yet let the encoder choose for you. For stereo HE should only be used with bitrates < 80 kbps. LC delivers better quality once the bitrate is high enough. HE is also less compatible. If a device only supports LC it will still play HE files, but they'll sound worse since you lose half the frequency range.

Keeping HD audio depends on what you want to do. The tracks have are usually several Mbps. DTS-HD in particular is most of the time > 3 Mbps because of the DTS core. If you want compatibility AC3 at 640 kbps is a good choice. If you care more about size use AAC. Both formats can deliver good quality.

[yetanotherid]

When it comes to DVD backups I just keep the original AC3 audio. There doesn't seem to be much point squishing it down. You don't save all that much space, it's time consuming and you can only lose quality.

"I don't know if i should stick with AC3 or go with AAC, my goal is to keep as much audio quality as i can while making a smaller audio file so i can give more quality to the video."

Does that mean you're restricting yourself to a particular overall file size? If so, can I ask why? Storage is pretty cheap these days. Personally I pick a quality (I generally encode DVDs at a CRF of 19) and just let the file size be whatever it needs to be.

[Carpo]

When it comes to DVD backups I just keep the original AC3 audio. There doesn't seem to be much point squishing it down. You don't save all that much space, it's time consuming and you can only lose quality.

"I don't know if i should stick with AC3 or go with AAC, my goal is to keep as much audio quality as i can while making a smaller audio file so i can give more quality to the video."

Does that mean you're restricting yourself to a particular overall file size? If so, can I ask why? Storage is pretty cheap these days. Personally I pick a quality (I generally encode DVDs at a CRF of 19) and just let the file size be whatever it needs to be.

I have always been used to doing 2 pass encodes, guess i am stuck in my ways, but i guess i can try CRF, seeing as i bought 2 1TB external drives for storage, what CRF do you use for bluray CRF 21?

Guess i will stick with original audio, as i did do some tests and i did not save that much on same tracks, between 8 to 10 meg which wont make any difference on the video quality

[yetanotherid]

I have always been used to doing 2 pass encodes, guess i am stuck in my ways, but i guess i can try CRF, seeing as i bought 2 1TB external drives for storage, what CRF do you use for bluray CRF 21?

I struggled for a bit to drag myself out of the 2 pass encode mindset when I switched to x264, but when I realised a single pass x264 encode while keeping the original audio was actually faster than converting a DVD to an AVI using 2 passes and MP3 audio, I never looked back.
I still encode AVIs for some of the other members of the household and still use 2 passes for some stuff but that's only to ensure standalone player compatibility as I don't think there's a way to limit the bitrate when using XviD and single pass encoding.

I haven't encoded a lot of HD stuff myself but CRF 20 would probably be my starting point. I use MeGUI which displays an estimated file size while encoding. It usually takes 10 minutes or so to settle down to something realistic, and if by that stage the file size looks like it's going to get out of hand I'd start again using CRF 21, but as I said I haven't encoded a huge amount of BluRay discs myself.

Which encoder GUI do you use? If you run a few 2 pass encodes using your preferred file size (or if you already have) you might be able to work out what sort of CRF was used for the second pass and maybe work out an average. It should be included in MeGUI's log files. If I remember correctly when encoding with HDConvertToX the CRF being used for the second pass is displayed in a command prompt window while it's encoding. I'm not sure about other GUIs.

[Carpo]

I use MeGUI and i have switched all the encodes i had set to CRF 19 as i am quite happy with the result :-) Will try a few blurays when i get home from the trip i'm on, i don't think the laptop will handle a bluray encode ;-)

[yetanotherid]

I use MeGUI and i have switched all the encodes i had set to CRF 19 as i am quite happy with the result :-) Will try a few blurays when i get home from the trip i'm on, i don't think the laptop will handle a bluray encode ;-)

I thought I was a little addicted to encoding stuff, but at least I don't take my encoding on trips with me. ;)

Edit.... Although then again..... I never go anywhere.....

[Carpo]

I bought some dvds and blurays while i am travelling, watched them and got bored, so thought i would encode them to break up the boredom ;) Thanks all for the information, much appreciated :)