How to mux three sources, but delay only two?

[hrpatton]

I've ripped a DVD so I can add an additional audio track to it. I want both the original and additional audio tracks to play simultaneously. (It's a RiffTrax commentary, if you're curious.)

I have the three files (.m2v, .ac3 and an mp3) and can mux them together, but FFmpegX doesn't have an option to delay multiple tracks. I need to delay the primary audio track and video track by 2:20 (14000 ms) to allow them to sync with the secondary audio track, which begins earlier. There will be "dead space" in which the secondary audio track plays for 2:20 before the video and primary audio track begin.

How can I do this?

[tomlee59]

I'm sure Case will chime in with a superior solution, but here's one option: Use your favorite audio editing tool (such as Audacity) to perform the time shifting. Then mux normally.

And I assume that you meant 140000ms (140 s). That's a much larger shift than I ever attempted in ffmpegx, so I'm not even sure that it could handle it. I'm not saying that it couldn't; I'm just saying it's well beyond anything I've tried.

Also, are you trying to produce a DVD-compliant stream? An mp3 track is not strictly allowed. If you want to maximize playability of the result, you may wish to transcode that mp3 into an mp2, say.

[Case]

Not a solution, but a comment: -

I want both the original and additional audio tracks to play simultaneously.

Multiple DVD audio streams can't be played simultaneously. In order to hear both audio sources at the same time, you'll need to mix them together into one audio stream with some sound editor, then mux that with the video.

2 min 20 sec is quite some delay. Do you plan on staring at a black screen for 02:20? Maybe it's easier to cut out 2:20 from the beginning of the commentary track and make that a separate title set, to be played before the picture starts.

[tomlee59]

I didn't read carefully (thanks again, Case); I just imagined that you wanted to be able to select either one. But yes, since you actually want to overlay one audio track on the other, you'll need to do exactly what Case described.

[hrpatton]

Not a solution, but a comment: -

2 min 20 sec is quite some delay. Do you plan on staring at a black screen for 02:20?

Yes, actually. There's audio commentary that precedes the video, so there's 2:20 of audio with a black screen. I suppose I could put in a background video for people to watch during this time, now that you mention it.

I've done as suggested and edited the two audio sources together in Audacity, then converted the resulting MP3 into an MP2. Now I'm unable to mux the video and my new audio file. The process fails in FFmpegX with this error:

**ERROR: [mplex] MUX STATUS: Frame data under-runs detected!

I'm not sure where/how I should fix this.

EDIT: OK, fixed the under-run problem by editing the audio file to be approximately the same length as the video.

Now, after muxing as a DVD, the resulting AUDIO_TS folder is empty, and there's no sound in the .VOB files in the VIDEO_TS folder.

*sigh* I think this may be over my head.

[tomlee59]

The AUDIO_TS folder normally *is* empty. All of the action is in the VIDEO_TS folder.

If the audio file plays fine by itself, but is only failing in the muxing/authoring stage, click the "invert mapping" option in the audio pane, and then mux and author. That might solve your problem.

[hrpatton]

The AUDIO_TS folder normally *is* empty. All of the action is in the VIDEO_TS folder.

If the audio file plays fine by itself, but is only failing in the muxing/authoring stage, click the "invert mapping" option in the audio pane, and then mux and author. That might solve your problem.

Wait ... the settings in the other panes effect the output of the Tools?

*donk*

I'm an idiot. <---- RTFM

Yes, the audio file plays fine by itself.

OK, assuming I have an MP3 containing my audio, and an M2V containing my video, how should I set up FFmpegX to successfully mux the files together into a working DVD?

I apologize for my lameness. I'm new to video/audio at this level, and I'm missing some basic concepts.

[tomlee59]

No, you are most definitely not an idiot!

I'm sorry that my terseness has confused you, so here's a somewhat more complete description of what I was suggesting:

Go back to the audio tab and convert your audio into another audio stream (it can have the same specs), but this time click "invert mapping" (although I don't think this is your problem, it's easy enough to try). If you want to stay compliant with DVD specs, the audio has to be sampled at 48kHz and be in MP2 format (I assume that when you typed MP3 in your most recent post, you really meant MP2. MP3 is not spec-compliant for DVD; if MP3is what you have, then that by itself would explain the difficulty you're having. Convert to MP2, and proceed from there).

Then use the Tools to mux and author.

Post back with more questions, or (hopefully) declaration of success.

--Cheers,

[hrpatton]

(I assume that when you typed MP3 in your most recent post, you really meant MP2. MP3 is not spec-compliant for DVD; if MP3is what you have, then that by itself would explain the difficulty you're having. Convert to MP2, and proceed from there).
--Cheers,

FFmpegX automatically generates an MP2 from the input audio file when muxing. I've tried both the files it generates and my own MP2s without success.

[tomlee59]

Could you describe in a little more detail what you did? For example, when you say that the mp2 that you create "didn't work," could you be more specific about the steps you took?

I'm assuming that the file you created with Audacity plays fine. Try different players, though, just to check. VLC, for example, is highly tolerant, and therefore may play streams that aren't actually fully spec-compliant. Try QT and see what happens.

As to ffmpegx creating MP2 automatically during muxing, I am not aware that it does so. Can you verify this by playing this created stream (again, in QT, say, or MPEGstreamclip)? Also take a look at the stream info to see if the players believe that the audio really is a valid mp2 audio file.

If, as seems to be the case, you really are trying to mux .m2v video with an .mp3 audio file, then all you have to do is first transcode the mp3 into an mp2 and then mux. You won't have a problem with this step as long as the elementary streams are individually compliant.

Can you post back with more details of what you've tried? It would also be instructive for you to post the output of the logifle (click on the blue "i" in the Progress window). That might help us give you more specific advice.

[hrpatton]

Could you describe in a little more detail what you did? For example, when you say that the mp2 that you create "didn't work," could you be more specific about the steps you took?

The VOB files created by the muxing don't have audio, either when played with VLC or when burned to disc.

The source MP3 plays fine in QT, iTunes et. al.

Can you verify this by playing this created stream (again, in QT, say, or MPEGstreamclip)? Also take a look at the stream info to see if the players believe that the audio really is a valid mp2 audio file.

Yep. FFmpegX creates "audio.mp3.mp2" when "audio.mp3" is supplied as the audio source for muxing. The created file remains after the mux, and it is indeed recognized as a valid MP2 stream by QT Player. The log shows that FFmpegX has used the converted file as the audio input for the mux.

I've also converted the MP3 into a working MP2 manually using FFmpegX, then used the MP2 as the audio source for the mux. The resulting VOB files are silent.

"Invert mapping" doesn't seem to have an effect either way.

[tomlee59]

Could you post the contents of the logfile from the Progress pane?

Also, when playing in VLC, say, you may have options for selecting audio tracks. If there are some, try them all to see if you get audio at some point.