AAC/MKV newbie: Probably basic questions but...

[lestatar]

All: First, I have been perusing this site for some time. Simply put, you folks here and at Hydrogen are the best. I can think of no other sites out there as informative and populated with so many knowledgeable folks. Kudos to all!

<sucking up over>

OK, my quick CV. I am an experienced tech manager with many years experience and I consider myself a good-above average poweruser, conversant with most everything tech - no way am I some kind of guru, but I get by.

But I am pretty conservative with my media formats. I like to play things safe and go with the formats most generally compatible even if they may not be the most cutting edge. I certainly know to stay away from horrid stuff like WMV, RM, RMVB, QT-MOV, etc...

My music is all LAME mp3s at fairly high bitrates or FLAC for archiving

Video: I tend to stay with AVI containers, usually encoded via H.264 or XVid.

I am familiar with most of the various transcoding utils out there, specifically MediaCoder, the new FormatFactory, and a ton of mp3/audio utils.

I am now starting to play around with MKV files and trying to better understand them without becoming an uber-expert.


My issue:

- I have a 4.38GB mkv of a concert DVD. I was able to successfully demux the mkv file and extract the AC3 audio track using mkvExtract [thanks to folks here].


I want to:

- burn the mkv onto a single DVD R disc. I have a few burner apps [not Nero because I feel it is bloatware despite their excellent tools]. The free and very competent CDBurnerXP claims to support overburning, but refuses to burn the file in this case. I am over capacity by a lousy 5MB! Any help/suggestions? Will I be forced to shrink the mkv file slightly using another app? I'd like to archive this concert on DVD.

- understand better the audio track system on this mkv. mkvinfo GUI tells me that there are 2 audio tracks in this mkv file. For movies, I am guessing that multiple audio tracks would contain stuff like commentary audio. But this is a concert DVD so I only am interested in the performance audio only.

I extracted one of the AAC ADTS tracks via mkvExtract and everything seems fine. I did notice that the resulting mp3 file was noticeably lower in volume than the one I got while using MediaCoder for the demuxing. Lame was used in both cases, identical versions/settings, no volume normalizing or gain applied. Any ideas why?

- which of the 2 audio tracks should I demux? I want the complete musical performance only. Will I have to use mkvExtract for both and then compare?

- convert whatever is the final and correct ac3 audio from the mkv file into high quality mp3 [around LAME V2 VBR]. I know how to do this, but need better understanding of the concept of channels. The mkv audio files show up as 6 channel. I don't have a home theater setup currently - main playback via DAP mp3 players, PC with speakers and subwoofer or through old school basic line in to a shelf system.


Should I transcode the AC3 into 6 channel mp3? Does mp3 even support this? Or is standard transcode into 2 channel stereo/joint stereo mp3 enough? I am more concerned with relatively good audio fidelity over stuff like 6 channel separation. Will I be missing anything? I am confused on this point and would greatly appreciate any help/clarity from the kind folks here.


That's about it for now. Again, I very much appreciate whatever help/advice you people can give.

cheers and happy holidays!
-lestatar

[midders]

If you're just trying to fit the mkv onto one disk, then use MKVExtract (as you mentioned) to extract all the tracks from the mkv file (use MediaInfo to identify the tracks easily) and then use MKVMerge to merge the video and single audio track that you want to keep into a new file. If you want to convert the audio track to another format first, then use FAAD to decode AAC to WAV (if necessary) and then eac3to to convert to AC3 (downmix to 2 channel using -down2 option).

Slainte

midders

[lestatar]

If you're just trying to fit the mkv onto one disk, then use MKVExtract (as you mentioned) to extract all the tracks from the mkv file (use MediaInfo to identify the tracks easily) and then use MKVMerge to merge the video and single audio track that you want to keep into a new file. If you want to convert the audio track to another format first, then use FAAD to decode AAC to WAV (if necessary) and then eac3to to convert to AC3 (downmix to 2 channel using -down2 option).

Slainte

midders

midders, thanks a million for responding and the info - I will try all your suggestions.

cheers and happy new year,
-lestatar

[minerva.thegift]

My best guess on the 2 audio tracks is that one is a higher quality than the other. As a basic rule, whenever a disc comes with a really high-quality audio track, it also has to have a lower quality one (that fits in with all the standards) to ensure that if someone's older player can't play the really nice track that it can at least play something. I've seen this more on Blu RAys than DVDs, but perhaps it applies here (I'm not sure.) Since you mentioned getting a better recording out of one track vs. the other, that's my best guess. Would you mind using a tool like MediaInfo and posting the details for your file, just so I (and the others here) can know exactly what we're dealing with?

As for 5 or 6 channel .mp3 files, check out this Wikipedia article. Basically it looks like a slightly modified .mp3 standard does support surround sound and since it's been around for over 5 years I'm guessing it should be fairly well supported. Of course I'd imagine muxing it down to 2 channels would give you a smaller file size that (in theory, at least) wouldn't sound any different on your given speaker set up.

[johns0]

Just load the mkv into mkvmerge and uncheck the tracks you dont need and save,not need to extract anything.Keep the main ac3 as is and uncheck the commentary.

[lestatar]

My best guess on the 2 audio tracks is that one is a higher quality than the other. As a basic rule, whenever a disc comes with a really high-quality audio track, it also has to have a lower quality one (that fits in with all the standards) to ensure that if someone's older player can't play the really nice track that it can at least play something. I've seen this more on Blu RAys than DVDs, but perhaps it applies here (I'm not sure.) Since you mentioned getting a better recording out of one track vs. the other, that's my best guess. Would you mind using a tool like MediaInfo and posting the details for your file, just so I (and the others here) can know exactly what we're dealing with?

As for 5 or 6 channel .mp3 files, check out this Wikipedia article. Basically it looks like a slightly modified .mp3 standard does support surround sound and since it's been around for over 5 years I'm guessing it should be fairly well supported. Of course I'd imagine muxing it down to 2 channels would give you a smaller file size that (in theory, at least) wouldn't sound any different on your given speaker set up.

Minerva: Happy New Year and thanks a million for your reply!

You make a ton of sense. I am sure you are correct with your deduction re: the apparent presence of both high and low quality audio sources since this is specifically a concert rip from a BDVD.

I have come to love MediaInfo [thanks to lurking here]. It has replaced sentimental fave GSpot - I should have posted the MediaInfo here originally but must have had a brain fart. Anyway, here is what I got:

General : W:\BillyIdol_InSuperOverdriveLive [2009]_720pBDRip.mkv
Format : Matroska at 9 160 Kbps
Length : 4 GiB for 1h 8mn 34s 27ms

Video #0 : AVC at 7 020 Kbps
Aspect : 1280 x 720 (1.778) at 29.970 fps

Audio #0 : DTS at 1 510 Kbps
Infos : 6 channels, 48.0 KHz
Language : en

Audio #1 : AC-3 at 448 Kbps
Infos : 6 channels, 48.0 KHz
Language : en


Thanks to all the comments here, I am starting to get a basic understanding of the mkv container format. My guess is that I should focus on demuxing the AC-3 audio track, downmixing [?] from 6 channels to standard 2 channel stereo and then convert to mp3.

But if that is indeed the case and the way I can get the "best" audio from the mkv, am I missing something by not using the DTS as the audio source? Or will it be irrelevant since I will lose 4 channels anyway going down to standard stereo?

Again, thank you so much for your comments and your help!

Still need to decide best way to reduce the mkv file size slightly so I can get it all on a single 4.38GB dvd. I guess if I demux the mkv into its 3 component parts, remove the DTS track and then remux with the AC3 track I will have no problem getting the new/final mkv onto a single DVD.

cheers and looking forward to your replies,
-lestatar

[lestatar]

Just load the mkv into mkvmerge and uncheck the tracks you dont need and save,not need to extract anything.Keep the main ac3 as is and uncheck the commentary.

Johns: Thanks and happy new year.

Yup, think you are spot on here on what I need to do [please see my reply to minerva]. In my case, instead of commentary, I think I simply need to uncheck the DTS track.

you folks are great.

cheers!
-lestatar

[minerva.thegift]

I'm glad that helped I think johns0 is right in that if you need to shrink the size just a bit, you can use something like mkvmerge and uncheck one of the audio tracks. That will save you from having to demux the whole thing out to its pieces then remuxing it back together - this way it'll just take out the part you don't need (so that you can save space.) If that doesn't save enough space, you might have to fight with converting the video (or perhaps the audio) so that you can make it smaller, but hopefully just removing one audio track will be enough.

As for getting a .mp3 of the audio, I don't think it should matter which track you use. I'm guessing your tools (like Audacity or something like that) will have better support for one over the other, but I don't know for sure - I don't generally play around with editing DVD/Blu Ray audio. In theory you should end up with an equally good (2 channel?) .mp3 from either source. Of course you'll find audio purists around here who will tell you to just keep it as it is or at least make it some sort of lossless format like .flac, but I am not one of those purists :P I generally can't tell much of a difference when using a lossy format like .mp3, so it doesn't really bother me. Especially since you don't have a full 5.1 or 7.1 surround sound set up and since you'll probably want to play it on some sort of portable .mp3 player/iPod-ish device, I don't see any reason not to convert it to just 2 channel in order to save space (and improve the odds that your device will be able to play it.) You might look around for guides or some other posts about AC3 or DTS -> .mp3 conversion, but I'm guessing it should be fairly straightforward.

[lestatar]

I'm glad that helped I think johns0 is right in that if you need to shrink the size just a bit, you can use something like mkvmerge and uncheck one of the audio tracks. <snipped>

Yup. This strategy definitely sounds like the way to go so I can archive the single mkv onto 1 DVD. What really stinks is that I am overcapacity by a measly 5MB...maybe I should bang my head and try and get some kind of overburning solution to work. cdXPBurner won't do it. I know Nero probably would, but I ended my love affair with it when it sadly became bloatware.

As for getting a .mp3 of the audio, I don't think it should matter which track you use. I'm guessing your tools (like Audacity or something like that) will have better support for one over the other, but I don't know for sure - I don't generally play around with editing DVD/Blu Ray audio. In theory you should end up with an equally good (2 channel?) .mp3 from either source. Of course you'll find audio purists around here who will tell you to just keep it as it is or at least make it some sort of lossless format like .flac, but I am not one of those purists :P I generally can't tell much of a difference when using a lossy format like .mp3, so it doesn't really bother me. Especially since you don't have a full 5.1 or 7.1 surround sound set up and since you'll probably want to play it on some sort of portable .mp3 player/iPod-ish device, I don't see any reason not to convert it to just 2 channel in order to save space (and improve the odds that your device will be able to play it.) You might look around for guides or some other posts about AC3 or DTS -> .mp3 conversion, but I'm guessing it should be fairly straightforward.

Again, your help is invaluable. This is exactly what I did and will do again, now that I am better informed. And I feel just as you do re: lossless formats. I am a closet musician and fancy myself as having above average ears, but with all due respect to the audio purists, I still maintain that a properly encoded mp3 using LAME will be nearly indistinguishable in blind listening tests to the ears of 95-99% of the population on earth, myself included. This is especially the case with the proliferation of portable DAPs as many people's main listening devices.

Of course, mp3 is not perfect - it is a terrific compromise, but a child born of necessity due to initial considerations of storage space. Now that HDD space is getting to the point where it is almost cheaper than dirt, lossless formats have become all the rage again. In my case, while my current home listening is basic 2.1 [above average PC speakers with a decent sub], at some point I will invest and go for a full 5.1 or better system. So I do plan to start future-proofing certain things - high quality, multi-channel concert performances from my favorite artists is likely where I will start.

So in this case, the ideal would be to keep everything as it is on the current single mkv file, but overburn to a single dvd so I have the "original". But for now, thanks to you folks, I have a better understanding of what I need to do so I can get what I want done.

ps: OT query...Just read some reviews on Thomson's mp3HD format and couldn't help thinking that this is mp3Pro all over again. They just won't give up will they? Any thoughts on mp3HD?

cheers and thanks again!
-lestatar

[johns0]

If you are trying to burn on a dvd+r and need an extra 5 mb of space burn onto a dvd-r,it has a bit more space than a dvd+r.

[lestatar]

If you are trying to burn on a dvd+r and need an extra 5 mb of space burn onto a dvd-r,it has a bit more space than a dvd+r.

johns: Thanks, but no dice. I only use dvd-r and still short.

<sigh> remember the good old days with VCRs when you could easily snip out on the fly stuff you didn't need by hitting "pause"?

cheers,
-lestatar