mpeg 2 audio

[vidmark]

I'm compressing a .mov file to a muxed mpeg2. The .mov file definitely has sound, and I definitely have audio checked on the preset, but the resulting .mpg doesn't have any sound. Can you point me in the right direction please? Thank you.vidmark

Posts: 1
Joined: Tue May 12, 2009 12:04 pm
Private messageE-mail

[guns1inger]

Using what software ?

What, exactly, is the source ? MOV is just a container, and could contain any number of video and audio combinations. The content may dictate the software you need to convert it.

What are you playing the file back with ? Are you sure you have the right codecs to play back the file you have created ?

[tomlee59]

Vidmark -- you're making a typical newbie assumption that we can read your mind. To help you, we need much more specific information than "I tried something, and it didn't work. What could be wrong?"

As guns1inger has asked, please tell us:

1) What are the characteristics of the source (codec types, frame rates, bit rates, etc.)?
2) What are the characteristics of the target format to which you want to convert the source?
3) What software are you using to attempt the conversion? What settings did you select?
4) What software/hardware are you using to play back the result and conclude that there's a problem? What settings, if any, did you vary in trying to solve your problem?

The more information you provide, the less mindreading we will have to attempt, and the more rapidly we'll be able to help you solve your problem.

[vidmark]

Thank you for your interest. I'm producing the .mov from Avid Xpress Pro - Avid DV Codec, 25fps, 720x576 PAL RGB. I'm importing into Sorenson Squeeze 5.0.1.1 - and producing a muxed (Program - one file for vision and sound) mpg. The video uses the MPEG-2 codec with the same settings as the .mov. The audio is set to the MPEG Layer 2 Audio codec with 224 kbps, 16 bit, 48khtz, stereo. These are the specs required by the broadcaster.
Sorenson will play the .mov fine, but will not play the resulting .mpg with sound (I also checked the file on another platform).
I appreciate your help.

[tomlee59]

Great -- that's useful information. So it appears that you are attempting to create an output mpg stream that complies with the PAL DVD standard.

Here are some things to try:

1) Play the program stream in VLC. See if there is more than one audio track listed. If so, see if any of them produces sound. Your problem could be as simple as an extra, spurious (e.g., alternate language) and non-existent track having been set as the default. The solution is to go back to your original muxing step, and make sure that the settings are correct (e.g., one audio track only, or at least set the correct track as the default).

2) If VLC doesn't find a playable audio track, try demuxing the program stream and playing the audio stream by itself. If there's still no audio, then the initial conversion into audio failed for some reason. If the audio does play, however, try remuxing and see if that magically fixes things. A surprising number of problems get solved by simply demuxing then remuxing, goofy as it sounds.

3) If the problem is in the initial audio conversion, then you'll need to post back with one more piece of information: What is the source audio's format? Is it the conventional (but not always followed) 48kHz 16-bit aiff/PCM?

You may also want to consider using QT (for example) to extract just the audio track from your .mov, and converting that separately into MP2, and then muxing that converted audio with the video stream that you're already happy with.

So, there are several possible ways to attack your problem.

[minidv2dvd]

skip the squeeze step altogether. rather than mov, have avid express encode to mpeg-2 from the source.

[vidmark]

Thank you tomlee59. I had never used VLC before - and the audio is there! It must be something to do with how I've got Sorenson Squeeze set up. [But it's strange that it will play a quicktime but not an mpeg?!] But thank you anyway - I can now send away the mpgs with confidence.

And thank you minidv2dvd as well - but Avid Express cannot export to mpg (although I am about to upgrade to Media Composer, so perhaps that will do it).

[tomlee59]

You may still have a problem, although not as serious as it could have been. VLC is a very capable player -- so capable, in fact, that it can sometimes make sense of damaged or noncompliant streams. So, playability in VLC is not a reliable guarantee that all is well. If VLC has identified extra, though blank, audio tracks, you may still want to fix things up. And if only VLC can play the result, I'd still be concerned that the final customer will have trouble.

If you know the final customer's actual setup, you might be able to test the clip with that combination, just to make sure that they will be happy.

In any case, congrats on getting this far. If further steps turn out to be needed, at least you know that they won't be too complex or time-consuming. And you might even be done already.

[minidv2dvd]

is that a mac limitation? pc versions render to mpeg2, i've used it in the past to do so.

Avid Xpress Pro software combines professional video, audio, film, effects, DVD authoring and encoding tools, plus custom music creation tools, for both Mac and PC, in one box. Its designed for professional editors looking for affordable, portable editing and creative tools. its perfect for students who want to create cutting-edge productions while learning the tools... More that define the industry. Editing features include multicamera clip grouping and ganging, one-touch and natural match automatic color correction, image stabilization with auto-zoom, pan and zoom of oversized stills and much more. Flexible formatting features include capturing and outputing native DV25 and SD media, mixing DV, SD, film resolutions in the same timeline and exceptional, high-quality export flexibility to formats such as WMV, MPEG 2, and Flash.

[vidmark]

Thanks tomlee59 - I should be OK - the broadcaster will let me know if it's not right. But I'll keep checking with the Sorenson situation.
And thanks minidv2dvd - but no, Im using P.C. It definitely can't export to MPEG 2 though the conventional export options.
Thank you both for you time and consideration.