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Export MPEG-2 without recompression
Sorry for posting again, but I didn’t get an answer for the last post, and I think it should be quite simple…
How do I export from PPRO MPEG-2 file, without recompression the whole video again (my source video is also MPEG-2, and I am going to make only small changes to it).
Is it possible in PPRO CS4 or in CS3 … ?Koby.
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15 Replies
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[Koby Goldberg] “I am going to make only small changes to it).”
What kind of small changes? adding any effects?
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Hi Brian,
Thank you very much for your repoly !I intend to replace several segments of few seconds each with different footage, and add some transitions. The whole video is about 1 hour, so most of it will stay the same.
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Good luck on not recompressing if you are doing transistions and adding other footage, most of the time AFAIK Ppro will recompress Mpeg, if you wanted to add like footage and just do cuts there is software that will do that without recompressing
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Brian,
Thank you for the reply!I know that for DV compression, PPRO has a feature for not recompressing (some checkmark on the export video options), isn’t there any hidden feature similarly for MPEG2… ?
I tried along time ago the MainConcept MPEG plugin for PPRO (for CS2 version), and it did just that: Upon export, it exported fast on any unchanged footage, and then would stop and actualy render slower on any changed/added footage. However the newer versions of MainConcept for CS3/CS4 doesn’t do that anymore… they recompress the whole video… That’s too shame they took out the best feature of their plugin!
I didn’t understand from what you wrote: Is there or is there not another software that can do it ?
Any other ideas … ?
Koby.
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There is no software that can take long-GOP MPEG and do any editing to it without recompression.
These clips are encoded originally as “Groups of Pictures” that are a given number of frames on length…12, 15, 20, etc. The first frame (the ‘I’ frame) is the only complete frame in the entire group. The rest of the images are derived from the I frame.
When you do even the most rudimentary cuts, you are shifting these groups and cutting pieces of them off.
For an easy example, let’s say you lay 2 seconds of 29.97 HDV onto an edit timeline. There would be four 15 frame groups in this clip. For you master edit, you decide you need 10 frames of black, then a 7 frame fade up…simple stuff. Now you want to export back to MPEG2…
However, now the first frame of the first GOP is not the first frame of your video…it’s a black frame, and it’s 10 frames earlier than you original first GOP I frame…which makes the original first I frame of the clip, frame 10 of the first 15 frame GOP…not to mention that every GOP thereafter is shifted and needs to be completely rebuilt taking frames that were not I frames and using them as I frames in the new GOPs that create the new exported clip.
…keep in mind I didn’t take out any frames or add any transitions. All I did was add ten frames of black and a fade to the beginning and recompression now has to take place.
So, the answer is, no…there is no software than can actually create edits in an MPEG stream and then re-export it to the same format without recompressing it. This is why intermediate codecs like CineForm and ProRes are popular with editors.
You can do it with DV and other intra-frame compressed formats because each frame is complete and separate and cutting the clips won’t change each frame’s structure, although even in these cases, any frames that have some effect or color correction applied, or are involved in a transition are still re-compressed.
TimK,
Director, Consultant
Kolb Productions, -
Hi Tim,
Thank you very much for the explanation.However from what I know the GOP size doesn’t have to be constant… it can change in the course of the DVD. This way commercial DVDs are made to achieve best quality: usualy each new scene (or camera cut) is starting a new GOP (with an I-frame).
Therefore in the example you gave, the first new 10 frames can create a GOP, the next 15 frames would be the second GOP (changed from the original because of the fade and would have to recompress), and the rest of the video could stay the same with it’s original GOPs.Moreover, I know it is possible because with an old MainConcept version (in PPRO CS2) I did it! I am not dreaming… 🙂 I realy did it. The export ran very fast on footage that didn’t change, and slowed down to render and recompress parts of the video that were added or changed. The time was 10:1 than the original video (if the video was 10min, the export to MPEG2 took about 1min), and that was on an older computer, so it could not have been a compression…
Koby.
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[Koby Goldberg] “Is there or is there not another software that can do it ?”
One is Videoredo.com it does frame accurate editing with smart rendering, I use it to touch up CITC recordings off of discs, its basically consumer software. -
[Koby Goldberg] “This way commercial DVDs are made to achieve best quality: usualy each new scene (or camera cut) is starting a new GOP (with an I-frame).”
If this is what you want to do, it’s not an NLE that does this…you need to add some other software to take care of that.
TimK,
Director, Consultant
Kolb Productions, -
Thank you very much Brian!
It looks great! I’ll look into that!
What exactly does it do ?
Is it like a Video Editor for MPEG files, that combines and cuts parts of it without recompression ?Tim,
What software did you mean ?
Something like Brian suggested ?p.s.: From what you both are saying, I understand that PPRO cannot do those accurate editting and smart compression… I hope that for AVCHD compression they CAN do it, because it would be quite a shame for someone to import AVCHD footage from a camera and need to recompress the whole video again after minor editting… (HD is much much slower)
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You could also look into Edius Procoder if it’s still around. From memory you can edit an mpeg then save out in the same format without recompression.
Lance
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