DXVA not functional with resolutions greater than 1080 on AMD GPUs

[Chipcraft]

AMDs fixed function video decoder engine (UVD) has supported H.264/VC-1/WMV decoding at 4K resolution since 5.0 version, which was introduced in Tonga ASIC. Since the launch of Tonga the decoder engine has evolved even further and the sixth version now support HEVC decoding at 4K resolution. The UVD6.x decoder was introduced in Wani (Carrizo SoC) and Fiji ASIC.

Currently all supported formats, on all ASICs (as listed previously) will fail to decode on ffmpeg through DXVA. All of the formats however can be decoded up to 1920x1080 resolution without any issues. Regardless of the format anything beyond this resolution will fall back to software decoder.

The DXVA acceleration works through Microsoft´s DTV DirectShow codec without any issues: H.264 has been validated at 4K in Windows 7 and HEVC has been validated at 4K in Windows 10 RTM with the same exact display drivers.

2.6 - 2.7.1 / master
built on GCC 4.9.2 / 5.10 (MingW)