Editing an MPEG2 file and burning it to DVD

[gzhawk]

Hi there. Any suggestions you all could provide to me would be greatly appreciated.


Here's my problem: I have a MPEG-2 movie that I want to edit, and then burn to a DVD. What is the fastest way to do this?


Here's what I'm currently attempting:

1. Convert MPEG-2 to DV. (I can get this to work, but it takes a while to run)
2. Import DV into iMovie. (Again, I have this working, but this takes a LONG time)
3. Edit movie in iMovie.
4. Burn DVD from iMovie through iDVD.


My question is: am I doing this process in the fastest/best way possible?


Here's some more information for you to help me:

Info on the movie:
From ffmpegX:
Video: mpeg-2, 480x480, 3500 kbps, 29.97 fps
Audio: mp2, 48000Hz, 192 kbps

From QuickTime Player:
Format: MPEG2 Muxed, 480 x 360
FPS: 29.97
Data Rate: 3684.78


Here is some more general info/issues regarding my situation:


* I have QuickTime Pro, with the MPEG2 Component installed.
* The movie opens fine in QuickTime Player, but when it plays, just the first couple of frames display, and then the video stops, but the audio continues fine
* VLC plays the video with no problems
* ffmpegX converts the video and audio to DV with no problems
* MPEG Streamclip opens the video just fine, but when I try to play it, edit it, or export the video, I get the same result as when I play it in QuickTime Player (first couple of frames of video, then just audio)
* The DV file that ffmpegX generates will import into iMovie, but at a rate of at least 1.5 times the length of the clip (i.e. it takes over 90 minutes to import a 60 minute clip), whereas a DV clip that I exported from iMovie, and then import back in will import at a rate of 0.1 times the length of the clip.


Again, here's how you can help me:

* Am I doing this process in the fastest/best way possible?
* Why does it take so long for iMovie to import my DV file?
* Are there optimal settings on ffmpegX for importing the result into iMovie?


Thanks in advance for any help you can provide.

[Frobozz]

If by editing you merely want to trim and cut segments then it is best to use Streamclip for this rather than convert to another format and re-encode. Try using Streamclip's Fix Timecode Breaks command in the Edit menu to get the entire video to display in Streamclip.

You also can do basic cutting and trimming of the DV video in QuickTime Pro without needing to import to iMovie. Importing to iMovie requires writing an additional copy of the DV video file.

Also, Toast lets you clip start and end points of DV video files.

[gzhawk]

Frobozz,

Thanks for the prompt response.

I tried the Fix Timecode Breaks command. This did not appear to have any effect.

I hadn't thought of cutting in trimming in QuickTime Pro, I guess because I couldn't cut and trim the raw MPEG-2 file in QuickTime. If I go this route, I guess I should edit the movie in QuickTime in a format that is possible to edit, yet will be a quick conversion back to DVD format to burn. Any suggestions for such a format, assuming that DV is not the best fit here?

If I find a good format, I think I'll just go this route, however, for curiousity's sake I'm still confused why one DV file imports into iMovie so quickly, while another does not? Any ideas?

P.S. I also have version 6.0 of Toast.

[tomlee59]

Make sure that after you fix timecode breaks, you save or export the result. Otherwise, the fix doesn't take.

If your problem is *data* breaks, then you need to go back and make sure that your splices occur at keyframe boundaries. If they don't, you will have many difficulties. Editing mpg is a pain because of this requirement. If the editing resolution imposed by this rule is too coarse, then you can still edit more finely, but at the expense of having to re-encode the result. Slowwwww...

[Frobozz]

Frobozz,

Thanks for the prompt response.

I tried the Fix Timecode Breaks command. This did not appear to have any effect.

Oh well, worth a try....

I hadn't thought of cutting in trimming in QuickTime Pro, I guess because I couldn't cut and trim the raw MPEG-2 file in QuickTime. If I go this route, I guess I should edit the movie in QuickTime in a format that is possible to edit, yet will be a quick conversion back to DVD format to burn. Any suggestions for such a format, assuming that DV is not the best fit here?

DV or full quality QuickTime movie will be your best bet. Everything else will take longer. I haven't done any conversions with 480x480 MPEGs (standard for SVCD) so I don't know what to expect.

If I find a good format, I think I'll just go this route, however, for curiousity's sake I'm still confused why one DV file imports into iMovie so quickly, while another does not? Any ideas?

There is the need to resample from 480x480 to 720x480 and that takes time. Plus, I believe iMovie has to render the video when importing. Apparently the rendering isn't needed when the video is from an iMovie export.

P.S. I also have version 6.0 of Toast.

Update to Toast 6.1.1. You can also use it to export to DV, but you have many other options for this as well.

[gzhawk]

If your problem is *data* breaks, then you need to go back and make sure that your splices occur at keyframe boundaries. If they don't, you will have many difficulties. Editing mpg is a pain because of this requirement. If the editing resolution imposed by this rule is too coarse, then you can still edit more finely, but at the expense of having to re-encode the result. Slowwwww...

When I fix time code breaks and then try to export, Streamclip gives me a data break message, so it appears I have data breaks. Your answer was a bit confusing to me. I'm not sure how to "make sure my splices occur at keyframe boundaries". Would you please be willing to offer a simpler explanation? Thanks.

[tomlee59]

Compressed video, like mpeg, doesn't actually encode each and every frame. Instead, only one of N frames is completely encoded. The rest are inferred from the frames that precede and/or follow it, using the assumption that things change slowly enough from frame to frame that you only need to encode differences (as one example; other things are going on as well). This saves space, but complicates edits, because you can no longer cut at any arbitrarily location. The completely encoded frames, known as key frames (or I frames in mpeg parlance), being independent of any others, are the only places where you can cut with impunity. If you cut elsewhere and then try to splice with some other random thing, you've messed things up rather badly because you've potentially removed data needed to reconstruct the non-keyframes. This is what causes data breaks.

Mpegstreamclip allows you to cut at right and "wrong" places, because it assumes the user knows about this limitation. To avoid this problem, use the "find keyframe" command in Mpegstreamclip, and make your cuts only at those locations. This means your editing resolution is very coarse (hundreds of milliseconds), but that's mpeg for you.

You can get around this limitation, but at the expense of an additional re-encoding operation.