fix: h264 level selection algorithm

[RebootVanChild]

There seems to be a slight issue in the h264 level selection algorithm. Widths and heights of frames and h264 macroblocks should be taken into account when doing the calculation, not only the pixel counts.
This issue can cause encoder invalid param error on certain resolution ranges.

For example, a 1922x1080 30fps video stream:

The correct algorithm should be

macroblocksPerFrame = Ceil( pixelsFrameWidth / pixelsMacroblockSide ) * Ceil( pixelsFrameHeight / pixelsMacroblockSide )
= Ceil( 1922 / 16 ) * Ceil( 1080 / 16 )
= 8228

Which resides in level 4.2.

However, according to current algorithm

macroblocksPerFrame = Ceil( pixelsPerFrame / pixelsPerMacroblock )
= Ceil( 1922 * 1080 / (16 * 16) )
= 8109

Thus, the algorithm would select level 4, and cause encoder invalid param error.

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[RebootVanChild]

Moved to PR #1049
Closing this because the author is not able to sign the CLA.