Comparing HDDVDs Burned from m2t and mpeg2 Files

[George Tyndall]

There isn’t a huge difference, but to my eyes it seems that a Blu-ray DVD that has been burned directly from the PRE7 m2t Timeline looks better than one that has been burned via an intermediate MPEG2 file (an MPEG2 file that has been created by using the File>Export>Movie command to export the m2t Timeline).

But, given that exporting an m2t Timeline as an MPEG2 file does not involve any change in resolution, shouldn’t the quality of the two DVDs be identical?

Related question: Given that the two formats are virtually identical, why does it take so long to export m2t as MPEG2?

[RJ Johnston]

I have a question. When you go File > Export > Movie, what codec do you pick and who manufactured it? For me there is no MPEG2 codec unless I go through FFDSHOW.

I can tell the difference between Blu-ray AVCHD and Blu-ray MPEG2. So adding another mpeg2 generation would make it even more noticeable, it would seem. There isn't any "smart rendering," where unedited video isn't recompressed. All the video is recompressed.

M2T > MPEG2 > AVCHD (recompressed twice)

vs.

M2T > AVCHD (recompressed once. This should be better)

[RJ Johnston]

I just remembered that when in a HD project that you can export to MPEG2 (as long as you don't export to something else first because the MPEG2 choice won't be there afterwards.)

[JohnnyO]

But, given that exporting an m2t Timeline as an MPEG2 file does not involve any change in resolution, shouldn’t the quality of the two DVDs be identical?

it has nothing to do with resolution. It has all to do with compression. Your timeline is getting heavily compressed when exporting to MPEG2. Then unless your software does smart rendering, that MPEG2 will get compressed again when burning to disc.

[George Tyndall]

it has nothing to do with resolution. It has all to do with compression. Your timeline is getting heavily compressed when exporting to MPEG2. Then unless your software does smart rendering, that MPEG2 will get compressed again when burning to disc.

Thanks for explaining why a Blu-ray DVD burned directly from the m2t Timeline should look better, as it does to me, than one that is burned from an intermdiate MPEG2.

What about saving an image of that directly-burned Blu-ray then later burning a second Blu-ray from that image? Should the first Blu-ray that I burned from the PRE7 Timeline look better than one that has been burned from its image?

[RJ Johnston]

The two should look the same, as the files on them are the same.

[George Tyndall]

The two should look the same, as the files on them are the same.

And that is my visual impression. Thanks for your reply RJ.

BTW, the reason I am exporting my PRE Timelines as MPEG2 is so, if ever I wish to combine a number of my 4- to 5-minute music videos on to a single DVD of about 1 hour in length, all I need do is import each of those MPEG2s onto a new Timeline with appropriate spacing prior to burning the DVD. In terms of DVD quality, is there a better way to do this?

[RJ Johnston]

Are these HD Mpeg2s or standard Mpeg2s.

The DVD, is that a standard DVD or a Blu-ray disc?

Whatever it is, I would try to find a video editor that won't recompress the MPEG2s. So I would make sure the MPEG2's that are exported can be "smart" rendered, that is they won't need to be decoded and then compressed again.

If you are exporting HD Mpegs for later use to burn a standard DVD, then it won't matter which video editor you use because you can't smart render because the video has to be resized.

[George Tyndall]

Are these HD Mpeg2s or standard Mpeg2s.

The DVD, is that a standard DVD or a Blu-ray disc?.

HD Mpeg2s for Blu-ray discs.

Whatever it is, I would try to find a video editor that won't recompress the MPEG2s. So I would make sure the MPEG2's that are exported can be "smart" rendered, that is they won't need to be decoded and then compressed again.

PRE7 is not such an editor? Can you give me an example of such a video editor?

Thank you!

[Paul LS]

Sony Vegas, Corel Video Studio, Pinnacle, PowerDirector... infact virtually every editor has MPEG2 smart-rendering apart from Premiere.

[George Tyndall]

Sony Vegas, Corel Video Studio, Pinnacle, PowerDirector... infact virtually every editor has MPEG2 smart-rendering apart from Premiere.

Paul, thanks for your reply. When you have time, I have a few questions:

1) Is PowerDirector part of the CyberLink suite?

2) Do I understand correctly that my goal in using a different editor than PRE is to end up with an uncompressed HD MPEG2 file that can be "smart rendered" for the purpose of making a Blu-ray DVD, in other words, will not require decompression, followed by recompression, to burn the DVD?

3) If that understanding is correct, then this question arises: Would the resulting Blu-ray DVD look as good as one that has been burned directly from my edited PRE7 mt2 Timeline?

4) I've read that editing an m2t Timeline in PRE7 is not as desirable as editing an "intermediate codec," something about the m2t format containing a Group of Pictures (GOP) that is 15 frames in length, and problems will arise if one cuts on the "I" frame. When you have time can you explain what that means?

[RJ Johnston]

The MPEG2 that you get when you go File>export>Movie from an AVCHD project in PRemire Elements can't be smart-rendered when trying to create a Blu-ray disc in Sony Vegas Movie Studio Platinum 9, Magix Movie Edit Pro 14+, or Nero 8 Vision. If on the otherhand you export by going Share > Personal Computer > MPEG > Mpeg2 1440x1080i, then that can be smart-rendered in Nero Vison to burn a Blu-ray disc (both audio and video 100% smart-rendered).

[George Tyndall]

The MPEG2 that you get when you go File>export>Movie from an AVCHD project in PRemire Elements can't be smart-rendered when trying to create a Blu-ray disc in Sony Vegas Movie Studio Platinum 9, Magix Movie Edit Pro 14+, or Nero 8 Vision. If on the otherhand you export by going Share > Personal Computer > MPEG > Mpeg2 1440x1080i, then that can be smart-rendered in Nero Vison to burn a Blu-ray disc (both audio and video 100% smart-rendered).

RJ, all my video projects consist of m2t video that I've created with a Canon HV30 using MiniDv tape. If I go the Share>Personal Computer>MPEG>MPEG2 1440x1080i route with PRE7, followed by using Nero 8 Vision to burn a smart-rendered Blu-ray disc from that file, will the DVD look as good as one that I have burned directly from the PRE7 Timeline?

Related question: I've read on this site that, if I install Nero 8, it may "lock on" to my Blu-ray burner and prevent me from burning a Blu-ray, and even a SD DVD, with PRE7. Any comment?

[Paul LS]

1) Is PowerDirector part of the CyberLink suite?

Yes, PowerDirector is part of the Cyberlink suite, the latest version will smart-render AVCHD as well as HD MPEG2/.m2t

2) Do I understand correctly that my goal in using a different editor than PRE is to end up with an uncompressed HD MPEG2 file that can be "smart rendered" for the purpose of making a Blu-ray DVD, in other words, will not require decompression, followed by recompression, to burn the DVD?

As an example. Smart rendering would be good for joining multiple MPEG2 files into a single project. If you do this with PE7 your multiple exported files will be re-rendered when exported/burnt from your final project.

3) If that understanding is correct, then this question arises: Would the resulting Blu-ray DVD look as good as one that has been burned directly from my edited PRE7 mt2 Timeline?

Yes, correct.

4) I've read that editing an m2t Timeline in PRE7 is not as desirable as editing an "intermediate codec," something about the m2t format containing a Group of Pictures (GOP) that is 15 frames in length, and problems will arise if one cuts on the "I" frame. When you have time can you explain what that means?

Frames in an MPEG compressed video are not stored sequentially and most frames are stored simply as changes from some prior frame (an I-frame is in effect a full "picture" frame). MPEG2 uses (typically) a 15 frame GOP (Group Of Pictures) where every 15 frame is an I-frame. If you do not cut on a GOP boundary (a GOP boundary is where MPEG has encoded a complete frame... I-frame) you can sometimes get issues such as green or blocky frames, this is because the frame may need information stored in nearby frames to complete the "picture". Therefore the editing software needs to take this into account to allow for edits to take place at any frame.

[George Tyndall]

Yes, PowerDirector is part of the Cyberlink suite, the latest version will smart-render AVCHD as well as HD MPEG2/.m2t....As an example. Smart rendering would be good for joining multiple MPEG2 files into a single project. If you do this with PE7 your multiple exported files will be re-rendered when exported/burnt from your final project.

Thanks for the detailed reply, Paul.

Problem is, I'm very comfortable with the PSE/PRE7 suite, and I've read that PRE is heads and shoulders above other semi-pro editors in terms of capabilities, so I'm reluctant to switch to a different editor. Hmmm. Dilemma!

Let's say I export my un-rendered PRE7 m2t Timeline, using the File>Export>Movie command, as HD MPEG2 1440x1080, and then I use, say, Power Director not to edit the movie but merely to burn a Blu-ray DVD from that MPEG2 file, would the resulting Blu-ray DVD look every bit as good as one that has been burned directly from the PRE7 Timeline? Or would I get a better result, as RJ has suggested, by exporting the Timeline using the Share Tab to create the HD MPEG2 file than I would by using the File>Export>Movie command?