For H.264 users, how to specify the Profile/level seems to be a fairly common. Profiles define sets of Bit stream features a H.264 stream can use. Levels define restrictions on the video resolution, frame rate and some stuff called-VBV (video Buffer Verifier).
H.264 Profiles
H.264 Profiles are discussed in depth on Wikipedia, but to simplify the considerations for the average user, I'll focus On the Baseline, Main and high Profiles. Baseline profile i/p slices multiple reference frames (–refs <int>, >1 in the x264 CLI) In-loop deblocking Entropy coding (–no-cabac in the x264 CLI) Main Profiles Baseline profile features mentioned B above slices Cabac c Oding interlaced Coding–paff/mbaff weighted prediction high profile Main profile features mentioned above 8x8 Option (–8X8DCT in the x264 CLI) Custom quantisation matrices
H.264 levels
H.264 levels are also discussed on Wikipedia, though in I opinion, less explicitly and less successfully for the pro Files. For practical use, to specify a level, a number of constraints have to be met.
The Resolutions/frame rates in the following table are merely a guideline–the number of macroblocks/second is the AC tual restriction. To calculate this:
Macroblocks are 16x16 in H.264 and so to code a frame one can calulate the number of macroblocks per frame as:
Ceil (width/16.0) * Ceil (height/16.0)
Note:the ceil () function rounds up its argument to the next integer. For example, Ceil (10.2) returns 11.
Then you need to multiply the number of macroblocks/frame by the number of frames per second to get the number of MACR Oblocks per second.
Macroblocks per second = Ceil (width/16.0) * Ceil (height/16.0) * frame rate
Level
VBV maximum bit rate [1000BITS/S]
VBV buffer size [1000bits]
macroblocks/s
resolution and Frame rate
1
64
175
1485
128x96@30 or 176x144@15
1b
128
350
1485
128x96@30 or 176x144@15
1.1
192
500
3000
176x144@30 or 320X240@10
1.2
384
1000
6000
176x144@60 or 320x240@20
1.3
768
2000
11880
352x288@30
2
2000
2000
11880
352x288@30
2.1
4000
4000
19800
352x288@50
2.2
4000
4000
20250
352x288@50 or 640x480@15
3
10000
10000
40500
720x480@30 or 720x576@25
3.1
14000
14000
108000
1280x720@30
3.2
20000
20000
216000
1280x720@60
4
20000
25000
245760
1920x1088@30 or 2kx1k@30
4.1
50000
62500
245760
1920x1088@30 or 2kx1k@30
4.2
50000
62500
522240
1920x1088@60 or or 2kx1k@60
5
135000
135000
589824
2560x1920@30
5.1
240000
240000
983040
4kx2k@30 or 4