[Tiles][Slices][Encode][ffmpeg_qsv][sample_encode] Tile encoding fails with default slice number setting

[fulinjie]

Testing on ICL with the latest MSDK version:

CMD:
./sample_encode h265 -i 1080p_blue_sky.yuv -o msdk.h265 -w 1920 -h 1080 -trows 1 -tcols 3 -n 10

ERROR:
libva info: VA-API version 1.6.0
libva info: va_getDriverName() returns 0
libva info: User requested driver 'iHD'
libva info: Trying to open /opt/X11R7/iHD/vpg_driver/lib/dri//iHD_drv_video.so
libva info: Found init function __vaDriverInit_1_6
libva info: va_openDriver() returns 0
Encoding Sample Version 8.4.27.

Input file format YUV420
Output video HEVC
Source picture:
Resolution 1920x1088
Crop X,Y,W,H 0,0,1920,1080
Destination picture:
Resolution 1920x1088
Crop X,Y,W,H 0,0,1920,1080
Frame rate 30.00
Bit rate(Kbps) 2890
Gop size 0
Ref dist 0
Ref number 0
Idr Interval 0
Target usage balanced
Memory type system
Media SDK impl hw
Media SDK version 1.30

Processing started
[CODEC]:CRITICAL - ExecuteSliceLevel:2436: MOS returned error, eStatus = 0x2
[CODEC]:CRITICAL - ExecuteEnc:4443: Slice level encoding failed.
[CODEC]:CRITICAL - Execute:587: MOS returned error, eStatus = 0x2
[LIBVA]:CRITICAL - EncodeInCodecHal:390: DDI:Failed in Codechal!
[LIBVA]:CRITICAL - EndPicture:81: DDI:DdiEncode_EncodeInCodecHal return failure.
sample_encode: /root/build/MediaSDK/_studio/mfx_lib/encode_hw/h265/src/mfx_h265_encode_vaapi.cpp:1760: virtual mfxStatus MfxHwH265Encode::VAAPIEncoder::Execute(const MfxHwH265Encode::Task&, mfxHDLPair): Assertion `0x00000000 == vaSts' failed.
Aborted (core dumped)

Same issue could be observed when enabling Tile Encoding support in FFmpeg QSV.

Analysis:
The number of Slices should be:
nSlice = std::max(nSlice, nTile);
However, it won't be resized if it equals to 1.(By default, the number of Slice is 1)