Video Passthru?

[Pawnslinger]

On some of the mp4 files that I have recently created with HandBrake, it would be desirable to go back and change the audio from ac3 to aac. I know that HandBrake can do this, but it would also transcode the video... right? No need for that. Is there some way to "passthru" the video, while transcoding the audio? If not, has it been suggested?

[TedJ]

HandBrake doesn't allow for video passthrough. It has been suggested on numerous occasions and consistently rejected, primarily because it makes it far more difficult to maintain A/V sync.

[Pawnslinger]

HandBrake doesn't allow for video passthrough. It has been suggested on numerous occasions and consistently rejected, primarily because it makes it far more difficult to maintain A/V sync.

Okay. So I guess that is not happening soon... if ever. I have found a program that will allow me to demux the audio stream and transcode to aac, but I can't seem to find a way to remux the audio. I will keep looking. But I guess that really is an invitation to audio sync issues too.

If I do a full transcode in HandBrake, how much do I lose in terms of video quality? Most of my videos are coded with RF=17.75, so hopefully I have some leeway there.

[TedJ]

You want to use one of the many mp4box GUIs to mux your AAC audio into your existing encode.

http://my-mp4box-gui.zymichost.com/

[Pawnslinger]

You want to use one of the many mp4box GUIs to mux your AAC audio into your existing encode.

http://my-mp4box-gui.zymichost.com/

I have tried 2 different GUIs for MP4box, and I couldn't get either to work. Yamb and something else... I have not been able to get the video demux'ed yet... if I could then I think I could use Yamb to rebuild the mp4. A lot of trouble for just a few files. I guess I will try a few thru HandBrake and see what they look like. I could also go back to the original copies, but I have already done that several times for other false starts... groan!

[GregiBoy]

If you used MKV's, to do this with MKVToolnix would be a piece of cake.....

[Pawnslinger]

If you used MKV's, to do this with MKVToolnix would be a piece of cake.....

I know. Using MP4 was a decision made based on other considerations. As was the decision to leave the ac3 audio in the the videos. Now, those decisions look not as good, but unfortunately circumstances still keep me using MP4.

My project has been a long one, and at many points along the way, I have gone back to square one and started over again, because I have learned along the way.

[musicvid]

Tried AVIDemux with your files?

[Pawnslinger]

Tried AVIDemux with your files?

Yes. It actually got a bit farther. I was able to start it, and tell it what to do (which I was clueless with the mp4box gui's). I found some instructions for having it do exactly what I needed, so I was hopeful. Then when I clicked "Save" or "Save As"... it started to do it, then crashed hard. When I restarted it, it told me it had crashed, and I said yeah, tell me about it. This happened 3 times and I figured it must be some sort of 64 bit 32 bit OS mismatch. Anyhow without further clues, I gave up on it.

[Pawnslinger]

I finally got MP4Box GUI to work... the version of MP4Box that came with it was the problem. I upgraded to the newer version and it now works. So I can demux/remux the video, using a conversion program in between times to change the audio to AAC. A lot of trouble, if one askes me.

And it may still have audio sync problems anyhow!

I did run a few back thru HandBrake, just to see what kind of lossy-ness I am looking at, and it seems to be in the 15-20% range. Not attractive either. No real good options.

I have looked all over the place, and I can't seem to find a program that can convert the audio in-place... without going to alot of trouble or transcoding the video.

[evs]

http://code.google.com/p/subler/ alows muxing and can transcode ac3 to aac

[TedJ]

It's also a OS X application.

[evs]

Oops…

Not sure if you are adverse to CLIs but if not you could try ffmpeg (exists for windows!). There might be a GUI for it.

If you just want a transcoded aac stream:

Code: Select all

ffmpeg -i in.mp4 -vcodec copy -acodec aac  out.mp4 -acodec copy -newaudio

If you want to have 2 audio streams: a transcoded aac stream and a copy of the original audio stream:

Code: Select all

ffmpeg -i in.mp4 -vcodec copy -acodec aac  out.mp4 -acodec copy -newaudio

[squal]

I give my thumbs up to Subler. Unfortunately is not multi-platform so I can't run it on my Ubuntu server, but I remux mkvs to m4v for the Apple TV with them (no re-conde of either audio or video). I'm sure they also work for the Xbox 360 if you install perian and convert the audio to aac stereo.

I still wish Hanbrake would have that feature. Muxing both streams into an m4v from another wrapper is pretty cool.

There's also PSP4Xvid on PC, but the mp4 files it creates never work with the Apple TV. Sometimes it works with Xbox 360, though.

[musicvid]

There are already many muxers available for any platform. Why would you want Handbrake to duplicate this, when it is already the best at what it does?

[squal]

Name me a tool as good as handbrake that can also mux video (or maybe one that just does that) into a compatible mp4 for Ubuntu and then I'll leave you alone.

I tried MP4Box to create files for the AppleTV and I failed miserably. It's not like I'm an MP4Box wiz, but I've read a couple of threads on the web where people where getting frustrated trying to do the same thing.

Is the problem just the fact that having this feature complicates syncing? So the results will be off 80% of the time, or something like that? Or is the problem that they don't want to add more features to not make it a jack of all trades and keep it simple?

They're both valid reasons, but that doesn't stop anyone from requesting that feature. That's valid too. If you claim that most handbrake users will never use that feature, when then you're probably right.

[Pawnslinger]

Here it is in a nutshell, I run Windows, so as nice as Subler may be... it is out of the question, for me anyhow. I have looked at several muxer type programs since I started this thread, and maybe I am just dumb, but I couldn't cut it with them. So I gave up, and learned to love the audio that I had. Someday, I will have to redo those videos from scratch, but not now. I wish HB had a passthru, but it doesn't. It would make life simpler.

[GregiBoy]

Your life would be a lot simpler if you used MKV's instead of MP4's.

[musicvid]

Are you guys having some problem with MakeMKV under Windows?
If so, you should take it up with them.

MakeMKV does what I want for muxing. Handbrake does what I want for compression, elegantly.
So am I just stupid, or are these really separate tasks??

[GregiBoy]

Nah, they're having problems with MP4's and remuxing.

I must be stupid too coz I see it the same as you. Different tool for different task.

[Pawnslinger]

Your life would be a lot simpler if you used MKV's instead of MP4's.

No. Subler would still be a Mac program, HB still would have no video passthru, and the devices I own that only play MP4 or MPG... well, they wouldn't have anything to play. So MP4 is what I must use, it is the common format across all my devices, and I have a lot of them (a family of 6 grown people use my server).

If it was just me, and just my WDTV, then I would use MKV in a heartbeat. But then I would leave the audio as AC3 and wouldn't need to convert!

[Pawnslinger]

Are you guys having some problem with MakeMKV under Windows?
If so, you should take it up with them.

MakeMKV does what I want for muxing. Handbrake does what I want for compression, elegantly.
So am I just stupid, or are these really separate tasks??

I don't have MKVs. I have a lot of MP4s with AC3 audio, that I can't play on devices that don't support AC3 audio. I was stupid, and I created a lot of these before I realized my mistake. So it was just a stupid mistake on my part.

[GregiBoy]

Have you tried AVIDemux under Windoze?

I use it ocassionally and it seems to work.

[Pawnslinger]

Have you tried AVIDemux under Windoze?

I use it ocassionally and it seems to work.

Yes. It crashed. I gave up. Don't worry... like Dr Strangelove, I have learned to love ac3 audio <grin>. Of course, Dr Strangelove learned to love the bomb. I am an old coote, so I know a lot of old films!