I-Frame

[CbSnakeCB]

Im kind of new to the capturing world and ive noticed some programs have a option called I-Frames. I was wondering what in the world this means and if it will help the quality of captures or anything, any help would be appreciated thanks.

[mrtristan]

I-Frames are Intracoded frames. This means that the frame is compressed, using only the data of itself.

P-Frames are Predicted frames and use the previous frame as a reference, when compressing.

B-Frames are Bilateral frames and are compressed by using the frames in before and after.

I frames have the least amount of compression. Next are P frames, followed by B frames.

Mpeg, mpeg2, and DivX are some file types that use I, P, and B frames.

[lacywest]

If you open a mpeg with only I frames ... in Virtualdub ... the sequence will be similar to AVI videos ... frame by frame. Makes video editing easier. More predictable editing and trimming.

Especially when your trimming the commercials off or when you've captured a GAC C\W music video and don't want the DJ appearing on the final video your making.

PowerVcr help file info:

GOP (Group of Pictures) Pattern
A MPEG compression technology, GOP concept reduces the temporal redundancy across frames (from frame to frame) for video content. There are three types of frames involved in the GOP concept:

I-Frame (Intra pictures): I-frame is typically the first frame of each GOP, is moderately compressed, and serves as the reference points for random access and can be likened to images.

P-Frame (Predicted pictures): P-frames are coded with reference to past pictures, predict in a forward direction and significantly compressed.

B-Frame (Bi-directional pictures): B-frames' predictions are forward, backward and bi-directional, which is relative to the other I-frames and P-frames. Compression is at a high level.

ATI Help file:

To select I-frame-only MPEG capture

This uses less CPU, but requires 2 to 3 times the bit-rate, which produces larger files.

Click the I Frames Only button. Click Next >, then click Finish.

To select I, B, P frame MPEG capture

This uses more CPU, but greatly reduces the bit-rate required to achieve good quality video. In Capture Wizard (Step 3),

Set Number of P Frames in Group to 12.
Set Number of B Frames in Subgroup to 3.

To achieve full 29.97 frames/second capture performance in MPEG-1 or MPEG-2 format, we recommend the following settings (ranges are given, as some video compresses better than others, depending on the amount of rapid motion and the number of complex scenes).


Video
Format IBP
Frames
(Mbps) Minimum
CPU
Required I-Frame
Only
(Mbps) Minimum
CPU
Required

176x144
QCIF 0.8 – 1.2 P200 -
MMX 1.2 – 2.0 P166 -
MMX

352x240
CIF 1.2 – 2.0 PII - 300 3.2 – 4.0 P200 -
MMX

352x480
Half-D1 2.0 – 3.2 PII – 400 3.0 – 6.0 PII - 350

640x480 3.2 – 4.0 PIII – 450 4.0 – 8.0 PII - 350

720x480
D1 3.2 – 5.0 PIII – 500 5.0 – 8.0 PII - 400

Mbps = Megabits (millions of bits) per second. 1 Mbps is approximately equal to 125 Kbytes per second.

TV Help v7.0.1 Copyright ©2000 ATI Technologies Inc.

[kimomakano]

I have an ATI All-In-Wonder 128 Rage Pro card and am using the software that it came with. If I select the I, B, P frames option, it only allows me to set P to 4 and B to 2.
What gives???
Thanks

[MOVIEGEEK]

I have an ATI All-In-Wonder 128 Rage Pro card and am using the software that it came with. If I select the I, B, P frames option, it only allows me to set P to 4 and B to 2.
What gives???
Thanks

I think whoever wrote the help files was smoking crack.I have ATI TV
Wonder and I capture with I,B,B,I and I'm able to put 2 extra minutes
on vcd with reduced blocks.I also set motion estimation search range to 256 hor. & 128 ver.

[The village idiot]

Mpeg links:

http://www.tektronix.com/Measurement/cgi-bin/framed.pl?Document=/Measurement/App_Notes...Set=television

http://bmrc.berkeley.edu/frame/research/mpeg/