Driver aborts when encoding H.264 at level 6 or higher

[fhvwy]

Setting level_idc to 60 (for level 6) gives:

ffmpeg_g: i965_avc_encoder_common.c:226: i965_avc_get_max_mv_len: Assertion `0' failed.
Aborted

[fritsch]

Level 6, 6.1 and 6.2 specify up to 8k surfaces. Currently all drivers are limited to a maximum of 4096 - does that need changing in above combination?

[fhvwy]

@fritsch The surface size constraint is already handled elsewhere - i965_CreateContext() blocks creating contexts for too-large streams.

(In any case, the 4096 limit is already insufficient for full support of level 4.2, which requires being able to handle a stream with width or height of up to 16*floor(sqrt(8702*8)) = 4208 pixels, and higher levels even bigger. Only levels up to 4.1 are fully supported.)