av1_argon_test1019 test fails with Assertion `dpbSlot >= 0'

[crmurillo]

This issue appears after fixing Issue #123.

Steps to reproduce:

$ /DEV/Vulkan-Video-Samples/BUILD/vk_video_decoder/demos/vk-video-dec-test -i /DEV/Vulkan-Video-Samples/tests/resources/video/av1/av1-argon_test1019.obu --verbose --enablePostProcessFilter 0 -o /DEV/Vulkan-Video-Samples/tests/results/decoded_av1_argon_test1019.yuv --noPresent

Failure:

vk-video-dec-test:  /DEV/Vulkan-Video-Samples/vk_video_decoder/libs/VkVideoParser/VulkanVideoParser.cpp:1808: uint32_t NvVulkanDecoder::VulkanVideoParser::FillDpbAV1State(const VkParserPictureData*, VkParserAv1PictureData*, NvVulkanDecoder::nvVideoDecodeAV1DpbSlotInfo*, StdVideoDecodeAV1PictureInfo*, uint32_t, VkVideoReferenceSlotInfoKHR*, int8_t*, int32_t*): Assertion ``dpbSlot >= 0' failed.

https://storage.googleapis.com/vulkan-video-samples/av1/av1-argon_test1019.obu

[crmurillo]

The frame sequence in this test case is:

Frame 0:

• frame_type: KEY, isKeyFrame: 1, refresh_frame_flags: 0xff, showFrame: 1
• Key frame will be shown, all the DPB slots will be refreshed, stored in picIdx 0.

Frame 1:

• frame_type: KEY, isKeyFrame: 1, refresh_frame_flags: 0x56, showFrame: 0
• Key frame will NOT be shown, only refreshes slots 1, 2, 4 and 6. Slots 0, 3, 5 and 7 should not be refreshed
• Stored in picIdx 1

Frame 2:

• frame_type: INTER, isKeyFrame: 0, refresh_frame_flags: 0xea, showFrame: 0
• Inter frame with refresh flags.
• References picIdx 0 and picIdx 1

When Frame 1 (showFrame=0) is processed, the reference processing loop sets picIdx = -1 for all slots because key frames don't need references for decoding. However, this is incorrect for DPB management: the pic_idx array indicates which pictures occupy the reference slots, and for hidden key frames (showFrame=0) with partial refresh_frame_flags, unreferenced slots must be preserved for future inter frames.

What happens:

• Reference loop sets picIdx = -1 for all 8 slots (because isKeyFrame = true)
• refDpbUsedAndValidMask remains 0x00000000
• ResetPicDpbSlots(0x00000000) invalidates all DPB slots
• Frame 0's DPB mapping is destroyed, even though slots 0,3,5,7 still reference it
• Frame 2 fails with assert(dpbSlot >= 0) when trying to use picIdx 0

DPB slots not being refreshed (slots 0,3,5,7 for refresh_frame_flags=0x56) should remain valid so subsequent inter frames can reference them.