Multi-trim in MF3 without re-encoding

[robinson]

I've read in many posts here that editing MPEG file in MF3 will re-encode the video. Does that also apply to multi-trim? I am asking because after doing few tests it seems there is no re-encoding. This is what I do and how I check the result -- could you please let me know if I am missing something?

My MPEG file is DVD compliant. MF3 options is set with "Do not convert MPEG compliant files" and "Treat MPEG audio as non-DVD compliant".

I select multi-trim and cut out parts I don't want. I do not create any menus. The resulting DVD files are written to hard-drive.

MF3 does show "Converting Video" message at the end, but I am not sure if this is re-encoding or transcoding. It is rather fast, just a bit longer than VideoReDo. Is it possible that MF3 is simply transcoding the video (I think that is what VideoReDo does)?

When all ready, I start a new project and load the VOB file to check the properties in MF3 (info button). Comparing it with the original MPEG file shows no change.

Is there any other way I could check if the file is being re-encoded?

Thank you,
R

[heinz-oz]

rest assured that your file is not re-encoded, not if it goes as quickly as you said. It will only have to re-encode if you add transitions, additional footage etc., even then, it should only encode non compliant mpeg files, original content that has not changed is not encoded. If it were, you would notice a deminished quality throughout since mpeg compression is rather lossy.

[robinson]

I will have to do some more testing over the weekend with longer files. Just wanted to know if it was at all possible that re-encoding doesn't take place because every single post I saw claimed that edit causes re-encoding. I wish MF3 had better documentation.

MF3 was bundled with my capture card (PVR-150). I already had Nero Vision Studio, but Nero would re-encode my captures because the audio was MPEG1Layer2 (it seems that this audio format is not valid for DVD-Video if it is the only audio stream). But MF3 doesn't have a problem with this audio format, although I think it does convert it.

[maddrummer3301]

>Is there any other way I could check if the file is being re-encoded?

If you Multi-trimmed the video, is the NEW video what you wanted.
Are the pieces missing from the video that you trimmed out?

As soon as you Modify the video it must be re-encoded using any
video editing program. That includes trimming/cutting/splitting/merging etc.

But, IF the project properties that you have set for the project are
EQUAL to the source videos then MovieFactory will use a technique
called "SmartRendering". SmartRendering is about 10-15 times faster than
re-encoding each individual frame to a new bit-rate.

If the resulting video is what you wanted then MF has used
"SmartRendering" to rebuild the timecodes etc in the mpg2 file.

VideoRedo uses smartrender.
MainConcept encoder(s) use smartrender.
WinDvd Recorder uses smartrender.
Many video programs use smartrender, VideoStudio, Dvd Workshop etc.

Many times though using smartrender an audio sync problem can
be created. That depends on how the video was recorded and
the program that is editing the video.

Hope this helps,

MD

[robinson]

MD, thanks for the description. And yes, I got the results I expected and without re-encoding it seems. But I don't think the project properties need to equal to the source video at all. I did two more tests -- I used the same video source for both:

Source is in CVD format (not VCD) and uses legal specs for DVD-Video: MPEG-2 video, 352x480, video data rate: variable 3,000 Mbps max, Audio is MPEG Layer 2, sampling rate 48,000 Hz, audio bit rate: 224 Kbps. (As far as I know only the audio portion is not legal for DVD-Video if it is the only audio stream.)

MF3 DVD Project MPEG properties were set in both cases as: 720x480, video data rate: variable 7,000 Mbps max, LPCM audio, 48 Khz

I did two conversions, using multi-trim edits in both. The only difference between the two was that one had "Do not convert compliant MPEG files" and "Treat MPEG audio as non-DVD compliant" selected, the other did not.

The one where the two options were not selected resulted in VOB output with the specifications as per Project settings, and it took a long time.

The other one that had the two options selected was very fast, but the MPEG properties were ignored and the result VOB output had the same video resolution and bit rate as the source. The only difference was that the audio was converted to LPCM and I think the audio bit rate was increased.

This is really a great news, since it would mean that I can use MF3 to remove commercials from the source without re-encoding.

[EDIT] I just tried doing this in Nero Vision Express since it has similar SmartRendering mechanism, but am not sure exactly what happened. The vOB file shows 352x480, but the video data rate is now max 9640 kbps, and the audio shows up as Dolby Digital. Maybe MF3 is not showing correct info for this VOB file? The Nero output was about as fast as the fastest MF3 output, but the size of the VOB that Nero Vision created is third smaller.

[UPDATE] The audio in VOB file from Nero is seriously out of sync, making in unusable. But I did another test with MF3, this time specified MPEG audio in project properties and turned off "Treat MPEG audio as non-DVD compliant" option. MF3 worked beautifully -- no reencoding of video and the file is as small as the one produced by Nero. No sync problems at all. I can't believe MF3 works this well...

R