working in premiere: saving video as codec DVX or as H.264

[nora]

Hi there,

I'm edditing some video's that I downloaded from youtube in premiere.
I am wondering why I should save the file as an .mov with the codec DXV? These are such a big files. When I save it as .mov with a H.264 codec it is much smaller (like 5 times smaller or something).
Is it because of how the quality of the video looks in resolume?
In that case I don't see so much difference. Or is it because DXV works better with effects on it?

Now I am saving everything as DXV (as recommended) but for example H.264 is allso good ofcourse I will do that.

Maybe I hear from you.

Nora

[Zoltán]

h264 is a very lossy codec, so if you re-encode an encoded and edited video, with every encoding you lose detail.(the higher bitrates are better, but produce larger files )
h264 works with keyframes, and difference data for the frames between keyframes, for a VJ this means that you can't simply jump to any frame, beacause if the frame is not a keyframe, the computer has to calculate the actual frame from the keyrame and diff data, and this takes time.
DXVs frames are all keyframes, so you can jump to any frame anytime without much effort.
h264 can't have an alpha channel as far as I know, DXV can.

for universal playback or files with alpha I would choose DXV, for achiving h264 with a high bitrate.
for linear playback, where you don't jump in the footage, and especially don't play backwards, h264 should be fine.

[nora]

Thank you very much! Again! This was usefull information.
Have a very nice day

[francoe]

DXVs frames are all keyframes, so you can jump to any frame anytime without much effort.

Nora, if you will enconde some clips to H264 anyway (lets say for saving space), try to lower down the "Key frame every x frames" setting of the encoder. If you use 1 as value means all are frames are keyframes (full pictures).
1 is ideal, but you can try set it to 2, 3 or even 5 (this means you have a full frame every 5 frames, etc). Will requiere a little more space than default H264 settings, but it will play a lot better.

My english is pretty bad, so take a look at this picture to get a clear idea.

Figure out how much processing is required to read frame 3 in first line where all are keyframes,
and how much in the second line, where you need to read the frame 1 and process the modification to get frame 3.

[Joris]

Aside from Francoe's excellent explanation, the problem with H264 is also just the decoding overhead.

Even if you set every frame as a keyframe, H264 expects that you're only watching a single video online. So it dedicates a lot of CPU power to just doing that. When I watch a single H264 encoded video in QT7 ( which is essentially the same as what Resolume does when you load a H264 video ), CPU usage jumps to 40%. 2 videos and I'm up to 87%.

Now imagine trying to play 4 or 5 of these videos in Resolume and what that will do to your poor computer.