editing codecs and mpg1/2

[dancray]

this topic has prol'y been discussed to death in various messages but I would like to ask a 2-part question please:

For reason too complex to get into, my current vid capture ability (without a hardware upgrade) using WInXp is limited to capturing video in only mpeg 1 or mpeg 2.


1: Is Mpg1/2 considered a poor codec when capturing for the intent to use your capture for video editing? Is huffy, mjpeg, etcetra quality all that better?

2: what video editing programs (if any) allow for the input and editing of mpg 1 or mpg 2 files?



thanks

[Dr Mordrid]

1. Yes, it can be painful to edit MPEG without hardware and drivers made for the purpose. Examples would be MPEG as done with cards like the RT-2000 or DV-1000.

The problem is that most MPEG captures are in the "IBP" format, which means only 1 frame out of 15 is a real bitmap (I-frame). The rest are mathematically calculated B and P frames. This 15 "frame" grouping of I, B and P frames is called a "Group Of Pictures".

This is why MPEG's are so small, but it makes them a pain to edit.

In order to edit IBP files with any efficiency at all they have to be converted to all I-frames by the editing software, which not all can do by default.

Even when the editor can do this it's still unwieldy, memory intensive and not very smooth as you have to get the exact video and audio bitrates and the GOP (IBP) settings on the money for the edit go well. If the MPEG uses a VBR (Variable BitRate) it's almost impossible to get it working smoothly as the bitrate changes constantly.

Another problem with MPEG as an editing codec: it's very lossy. This means that when you add effects, titles etc. you are likely to get artifacts due to the recompression of the data. MPEG handles recompression far less cleanly than all I-Frame codecs like MJPeg.

Because of the above MPEG is far better used as an export format.

2. MSPro 6.5 can capture, load, edit and export MPEG within the limitations listed above. Getting the project settings right for editing is tricky, as noted above. It's little brother, VideoStudio5, also supports capture, editing and exporting MPEG but it's less configurable than MSPro 6.5.

Premiere6 can load MPEG files, but using it to edit is painful as it then has to recompress the video to whatever the project setting is before it'll do full speed previews or export the video. This is because Premiere6 has no native MPEG support in terms of project or export settings.

I recently loaded a DVD format MPEG of 30 minutes into Premiere6 as an experiment and the timeline conversion to a PICVideo MJPeg project setting for previewing took almost 4 hours.

Dr. Mordrid

[dancray]

looks like I will be buying a proper capture card, thank you Dr. M.

[IM_Riktar]

What about I-frame only capture?

Hey Doc,
While I was building/playing with a new system that was using a AIW Radeon I noticed one of the capture options listed I-frame only capture which I didn't have the time to try.

Anywho, Would I be correct in assuming that this would provide an editable capture file since the "B & P's" would be left out of the equation? And if it did would it still be burnable and playable after editing into SVCD format for standalone DVD playing?

I wish I hadn't been in such a hurry to build that box and get it out the door. Methinks that when the unit comes back for it's dual CPU upgrade I am going to take my time with completing the upgrade. For the sake of trying out the I-Frame only capture. Unless you can explain why I am full of beans with this theory.