PDA

View Full Version : MPG Problem



riki
06-17-2003, 11:50 PM
I don't normally work with video, so I don't have a lot in terms of video editing software or hardware, or much knowledge in this area.

Anyway one of my clients has given me an Mpg file (MPEG1??). I need to break the file up into three segments, but when I try to open it in Quicktime Pro all the Edit menu options are ghosted over. I've discoverred that I can Export the MPG as a Mov file and then work with it in QT Pro but I'm loosing the audio.

I think my only option is to get the client to come back with a Mov file. Anyway to cut a long story short I'm just worried if this is the right way to go and what formats I should save it in for the web. It's intended to be uploaded to the clients website and will need to be viewed by PC and MAC users. Compression is also an issue. Currently the file is about 93Mb and I need to compress this down significantly.

Any advice would be much appreciated.

Beamtracer
06-18-2003, 12:49 AM
Hi Ricki. I'll see if I can help...

For cross platform movies, nothing beats Quicktime. Quicktime Pro is great to use for compression.

Common codecs for small file sizes:
(Larger file sizes top of list, smaller at bottom)

Photo JPEG _ _ _ _ Plays in QT 3,4,5,6

Sorenson - - - Plays on QT 4,5,6

Sorenson3 - - - Plays on QT 5,6

MPEG-4 - - - Plays on QT 6 only

These codecs work in either Mac or Windows versions of Quicktime. Maybe ask your client to make sure they've got QT 5 or 6 installed, then you can make the file sizes smaller. I'd recommend you use either Sorenson or Sorenson3 to email to your client.

A tip for small sizes... in the QTpro options, some of the codecs have a setting for 'Key Frames'. Set this to a high number, like 100 or more.

A key frame is a complete frame. Between key frames QT only updates the pixels that have changed, so that's how it saves space. The downside is if you move the timeline and jump to a frame in the middle, QT must cache all the previous frames until it hits the previous key frame. That means it'll be a second or two before it'll display the frame.

Reduce quality. I always make a master copy of my movie in something like Animation codec (big files, lossless). Then I use QTpro to export to other codecs. Keep reducing the quality settings and increasing the keyframes to see how far you can go before the quality becomes too bad.

Make the screen area smaller. The full video size (NTSC 720x480, PAL 720x576) is too big for the web. The client probably won't be able to play it back smoothly. Half it and it'll play back better.

Is your video interlaced? Jagged edges?

I don't know why you're not getting audio. Did you tick the little check-box for audio in the options panel? Hit command+I to get info and see what information you can get about the audio track.

The 'Get Info' command is also useful to check your video file. It's probably an MPEG-1 you have. The free QT doesn't play MPEG-2, and QTpro only plays it if you have purchased the MPEG-2 codec from the Apple Store.

A plain MPEG-4 in most cases has the .mp4 suffix. A Quicktime '.mov' can also use MPEG-4 codecs, and is basically the same thing. The difference between the two is that the '.mov' can incorporate other file types as well.

riki
06-18-2003, 01:15 AM
Thanks Beam I'm going to give that a try.


I don't know why you're not getting audio. Did you tick the little check-box for audio in the options panel? Hit command+I to get info and see what information you can get about the audio track.

No I wasn't able to tick this box in the option panel, it's ghosted over. Even though the MPG file obviously has audio. Apparently it's not avaliable because there isn't an audio track.

Not sure how that works??

Beamtracer
06-18-2003, 02:54 AM
Have you been able to hear any audio? If not, there probably is none in the MPEG file.

In QTpro, go to the 'Movie' menu on the top menu bar. Then select 'Get Movie Properties' (Command+J).

A dialog box will come up. On this box there are two pull-down menus, 'Movie' and 'Annotations'. Click on the 'Movie' pull-down menu, and see what choices there are. It should say something like this:

Movie
Sound Track
Video Track

If it doesn't say Sound Track, then this file has no sound. Whoever sent it to you didn't include any sound.

Alternatively, if you can hear sound, double check those grayed out settings in the Option box, and see if you can still click the sound option (as below)

riki
06-18-2003, 03:15 AM
Hi Beam

Thanks again for your help. This is the settings for the MPG, it does have vocal audio which you can hear during playback. But it's not coming up in the Options panel.

Beamtracer
06-18-2003, 06:12 AM
Ah, here's your problem:

Muxed audio is when the video and audio are multiplexed into a single channel. This is why Quicktime Pro can't separate it.

You'll first have to go to another application to extract that audio.

Go to VersionTracker.com and search for MPEG-1 audio extractors that work in OS9.
http://www.versiontracker.com/mp/new_search.m?productDB=mac&mode=Quick&OS_Filter=MacOS&search=mpeg+1&x=0&y=0

Extract the audio, then you can join it back on to the QT vision in QTpro.

It's a total pain in the butt that someone sent you muxed audio. Especially as they want you to edit with it.

By the way, Apple's MPEG-2 component (which can be purchased from the Apple Store) can extract muxed MPEG-2 audio, but not MPEG-1. You'll have to look for something else (or get your client to resend).

riki
06-18-2003, 06:54 AM
uuugggh bloody New Zealanders :) Okay I'm going to get them to resend it. Thanks again for your help.

Beamtracer
06-18-2003, 08:27 AM
Get them to send it as a Quicktime movie if you can. Don't use MPEG-1 or it might happen again.

Quicktime Pro can accept a lot of formats and codecs. Here is the list from Apple:

http://www.apple.com/quicktime/products/qt/specifications.html

riki
06-18-2003, 08:45 AM
Will do, thanks for that.