Converting AAC audio to AC3

[carlmart]

Which is the best way, in speed and quality, to convert a 5.1 AAC track onto 640K 5.1 AC3?

[aedipuss]

the best way would be to use whatever audio/video editor you have. have to ask why though? 640 isn't allowed on a dvd and converting is just reducing the audio quality with a re-encode.

[yoda313]

640 isn't allowed on a dvd

Maybe the destination isn't a dvd. You could do 640kbps on an avchd can't you? And you could do it as a file with h264 in an mp4 or mkv file without worrying about dvd specs.

converting is just reducing the audio quality with a re-encode.

NOrmally I'd agree with this statement my guess here is that the poster is going to use the aac surround file on an amp that doesn't do aac surround natively. Hence the encoding to ac3 to make it compatible. That would be worth the encoding.

[carlmart]

I'm sorry not to have been more specific.

The final destination is an MKV file, partnering with a 720p file. So bit rate is not a problem.

This is the first time I find AAC with a high quality 720p video, and I don't know why they did it. My player does not play AAC files from discs, so I need to convert them.

In the meantime I gave it a try with FLV MP3 converter, which allows what I wanted.

Unfortunately when I merged the new mkv file, the VIDEO did not play and the audio did.

So now it seems the video has some kind of incompatibility with my BD player. The strange thing is that I compared that video specs with another 720p video I had, and it seems to have similar specs.

If I put the Mediainfo specs here, can someone tell me what might be happening?

[yoda313]

Use eac3to to convert the audio.

[manono]

And MKV2AC3 is a GUI for eac3to (and Aften) that doesn't require you to demux/remux yourself.

[carlmart]

Can we move this thread to video conversion?

My audio problem, as I mentioned above, now has turned into the video problem I seem to be having.

[poisondeathray]

did you disable header removal compression in the mkvmerge options? It can cause playback issues with many standalone units

[carlmart]

Yes, I did remove the header two times: first when I replaced the AC3 instead of the AAC, and it didn't play; second when I simply removed the header stripping, leaving the AAC, and it didn't play either.

I am quite used now to removing the header, even if it comes only in about 10% of what I download.

[poisondeathray]

Yes, I did remove the header two times: first when I replaced the AC3 instead of the AAC, and it didn't play; second when I simply removed the header stripping, leaving the AAC, and it didn't play either.

I am quite used now to removing the header, even if it comes only in about 10% of what I download.

Are we referring to the same thing ? I'm not talking about removing the header; I'm talking about disabling header removal compression.

[aedipuss]

mkvmergegui

[carlmart]

I think we are talking about the same thing, though in my version (4.9.1) it's done a bit differently.

Extra options > compression > none.

That is done for video and audio tracks.

As I said it's how I remove header stripping.

[poisondeathray]

Try a different version; either recent or very old

Or use a different container like transport stream

[carlmart]

Try a different version; either recent or very old

OK. Re-merged with version 5.7.0, deleting compression on video and audio tracks, eliminating all other tracks, and the problem remained the same.

Or use a different container like transport stream

How do it that? Use which other transport stream?

This is what my video is now:

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High 10@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 8 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 1h 53mn
Width : 1 280 pixels
Height : 592 pixels
Display aspect ratio : 2.2:1
Frame rate : 24.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 10 bits
Scan type : Progressive
Writing library : x264 core 125 r2208 d9d2288
Encoding settings : cabac=1 / ref=8 / deblock=1:-1:-1 / analyse=0x3:0x133 / me=umh / subme=9 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=24 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=crf / mbtree=1 / crf=19.0 / qcomp=0.60 / qpmin=0 / qpmax=81 / qpstep=4 / vbv_maxrate=150000 / vbv_bufsize=187500 / crf_max=0.0 / nal_hrd=none / ip_ratio=1.40 / aq=1:1.00
Matrix coefficients : BT.709-5, BT.1361, IEC 61966-2-4 709, SMPTE RP177

[poisondeathray]

Format profile : High 10@L4.1

It's 10bit avc . No hardware players support it.

[carlmart]

Thanks. I guessed there had to be a catch.

[yoda313]

Thanks. I guessed there had to be a catch.

Even if you have to convert the video (which will necessitate a loss in quality - albeit probably not much depending on what you do to it) you probably will still have to convert the aac to ac3 for proper playback. Just keep that in mind going forward if you intend to use this source in the future.

Also if this was created by you please note just like anything its best to hit your target the first time to limit conversions. Check your playback hardware requirements and make sure you hit them as closely as possible so you don't have to incurr lossy conversions. Of course trial and error is often involved so pack some patients and use rewritable discs or flash media to save on expensive media (if doing it to bluray recordable use a rewritable ).

Good luck.