AC3 to AAC using MeGUI

[john3voltas]

Hello there.
I have a couple of Disney movies I would like to backup to MKV/MP4 and, while I still have access to a Windows computer, I was thinking about doing that using MeGUI.
Original audio is AC3 5.1@448kbps.
I was wondering, what is the usual way people go about it? Do they keep the 6 tracks or do they convert to stereo?
Should I do an FFmpeg MP2 conversion? Should I do a QAAC AAC conversion?
What do the warez release groups usually do? Not that I want anything to do with them but they seem to please the big masses, right? So whatever they do it seems to work with most people. I guess...

[hardy]

AC3 448kbps is the standard for DVD.
Converting that to a lower bitrate is a bad idea.
AAC is not better by any means, nor is the container MP4.

[Detmek]

If you want to save some space you will have to downmix to stereo and encode at TVBR 63 at least using QAAC or q 0,4 using Nero AAC encoder. That will give you bitrate around 128kbs+/-20kbs. Saving 6 channel audio even in AAC format will not save you enough space but you will loose a bit of quality.

[john3voltas]

Well, reading your answer I get the feeling that I must explain better and rephrase a bit of what I wrote before.
I may have mislead you a bit when I used the word backup.
What I intend to do is rip the original DVD, reencode it to something that most media players can read these days (x264/aac or similar) and put the original DVD back in the box and store it away from kids to make sure it doesn't get any scratches or that it doesn't disappear.
Due to the fact that there will be reencoding I am aware that I will lose some details both on image and on audio. I can live with that.
I was wondering on what people use these days. I've heard that people downsample AC3 5.1 into AAC stereo. Since I don't have a 5.1 system I guess I could live with that.
So, what would be the proper instructions to do an AC3 5.1 to AAC stereo using MeGUI with QAAC?
Do you recommend anything else given the task at hands?
Thanks in advance and sorry if I mislead anyone.
Cheers

[Detmek]

So, what would be the proper instructions to do an AC3 5.1 to AAC stereo using MeGUI with QAAC?

Most media players support MP4 and MKV so choose whatever format you like. I usually go with MKV because one of my players has problem playing MP4 files longer then 2,04 hours. And I don't play files on mobile devices.

For audio encoding settings you can do something like this:

[john3voltas]

@Detmek
Sorry, on my previous post when I wrote "reading your answer" I was trying to address user 'hardy' only.
I missed your first post and I only noticed it when I read your second post.
So, If I want to save space at the expense of quality but not fully compromising quality I could go with downmix to stereo, LC-AAC, TVBR and Q63 at 44.1khz.
BTW, how do you compare both NeroAAC/QAAC? Which one would you choose for this purpose?
Cheers

[Detmek]

Those are very similar about quality. Nero AAC is no longer developed but is still very good. QAAC, which is frontend for Apple AAC encoder is best AAC encoder for encoding music, according to tests at Hydrogenaud.io forum.

Personally, I use QAAC (Apple AAC encoder) for music and movies because it is still in active development.

NeroAAC is easier to "install". You just need .exe file in right directory. For Apple AAC you need to install iTunes or use BAT script to extract corect files and put it in same directory as qaac.exe.

So, QAAC with TVBR q63 or little bit higher, or NeroAAC q 0,4 or little bit higher, Stereo and 44,4kHz is just fine for encoding movies. x264 with preset Slow and CRF 20 or little bit lower should give you good compromise between filesize and quality.

P.S. If your DVD video is interlaced, don't forget to deinterlace.

[hello_hello]

So, If I want to save space at the expense of quality but not fully compromising quality I could go with downmix to stereo, LC-AAC, TVBR and Q63 at 44.1khz

Is there a reason you'd change the sample rate rather than leave it at 48k?

[john3voltas]

So, QAAC with TVBR q63 or little bit higher, or NeroAAC q 0,4 or little bit higher, Stereo and 44,4kHz is just fine for encoding movies. x264 with preset Slow and CRF 20 or little bit lower should give you good compromise between filesize and quality.

Hmmm, those Presets. I knew I'd read something about those. Are these it? https://forum.doom9.org/showthread.php?t=139765
Cause I don't see a Slow or a CRF on that list.

P.S. If your DVD video is interlaced, don't forget to deinterlace.

Nah, this is PAL land, quite sure these sources are all plain progressive but thanks for bringing that up.

Is there a reason you'd change the sample rate rather than leave it at 48k?

No, not really. To be honest, I was just summarizing what Detmek had just wrote.

[hello_hello]

john3voltas,
The x264 presets you linked to are old and obsolete. x264 has it's own speed presets. The default is medium, but I use slow or slower mostly myself. You can select a speed preset using MeGUI's encoder configuration. There's also an option to select an x264 "Tuning" such as "None", "Film" or "grain" etc. If in doubt, go with "film".
The CRF value specifies a quality for single pass encoding. In MeGUI's x264 encoder configuration it's the "Targeting Quality" option. The value you select is the CRF value. CRF 18 is roughly where the encoder is considered to be transparent at normal viewing distance. Higher CRF values = smaller file sizes and lower quality, but anywhere between 18-20 should look very good. I tend to use CRF18 for 720p and lower resolutions and CRF20 for 1080p.

As a quick trial, I picked a stereo ac3 file I had handy (from a TV show, predominantly speech) and encoded it with QAAC's True VBR, q63, then again while resampling it at 44.1k. The birate only dropped by 3kbps (97kbps vs 94kbps) and for a 1 hour file the file sizes were 43.6MB and 42.4MB. Resampling doesn't seem to achieve much.

I don't normally convert audio myself unless it's DTS. For stereo AC3 it's not worth it, especially if you use the default QAAC VBR quality as I do (q91). The AC3 file I converted above was 142MB, but a 100MB reduction isn't much in relation to the video size. If you're downmixing 5.1ch AC3 to stereo you'll see more of a benefit, although even then I just keep the original AC3 myself.

[john3voltas]

Sweet! Thanks @hello_hello I didn't know the recommendation now was to use x264 owns presets based on speed of encoding and quality of the source.
I can still remind seeing stuff like

 cabac=1 / ref=8 / deblock=1:-2:-2 / analyse=0x3:0x113 / me=umh / subme=9 / psy=1 / psy_rd=1.00:0.25 / mixed_ref=0 / me_range=32 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=6,6 / fast_pskip=0 / chroma_qp_offset=-4 / threads=24 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=0 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=4 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=2pass / mbtree=1 / bitrate=2560 / ratetol=1.0 / qcomp=0.00 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=20000 / vbv_bufsize=25000 / nal_hrd=none / ip_ratio=1.10 / aq=1:1.00

As for CRF, you're talking about the "Quality" setting between "Encoding Mode" and "Tuning", right?
As for the audio sampling rate, I might stick to 48Khz since your experience shows almost no gains from downsampling to 44.1Khz.
Thanks a lot for your input.
Cheers

[hello_hello]

As for CRF, you're talking about the "Quality" setting between "Encoding Mode" and "Tuning", right?

Yes.

Another option, if you have plenty of hard drive space, might be to not re-encode anything. MakeMKV will rip DVDs and put the video and audio etc in an MKV container, so there's no quality loss. Once it's ripped you could put it in another container if need be. TSMuxer will remux MKVs as TS files. If your media player doesn't support mpeg2 in an MKV container it'll probably be fine with TS files.

[john3voltas]

Yea, space is scarce so I'll have to go lossy here.
But MakeMKV is an option too. Not the best because as far as I know it's closed source. I'd rather go with handbrake or something more open.
Not that I'm closing the door on closed source at all. I'd happily go with closed source as long as it's more reliable than the opensource alternative.
MakeMKV would containerize the audio/video. I'd have to demux it to reencode an remux it again. Not a big deal.
My player is a couple of Raspberry Pi's running XBMC 17.3 (kodi). This hardware only has mpeg2 hardware decoding if I buy a license. But I will go with x264 anyway because it's smaller in the 1st place.
Thanks for the tips.
Cheers