SK-AM62P-LP: Gray figure occurs at room temperature and the bit rate is out of control in special scenarios

Hi Qinghong,

Gray color appearing on screen has been fixed in the newer driver version. See below commit.

https://git.linuxtv.org/media.git/commit/drivers/media/platform/chips-media/wave5?id=6bae4d5053da634eecb611118e7cd91a677a4bbf

 As you are using an older version, please add this to the existing driver, rebuild it, and deploy to your environment.

Best Regards,

Suren

Hi Qinghong,

To regulate the Bitrate, we have tried these parameters and here are few things that you could try and change.

• set V4L2_CID_MPEG_VIDEO_MB_RC_ENABLE to 1
  • Will enable CTU level RC (rate control) as well
  • CTU is lowest level of processing in HEVC, enabling RC here allows the most granular control over QP and bit allocation
• Choose a lower level
  • From the e2e I see that they are using a bunch of different resolutions
  • For the lower resolutions (640x864, 448x608), they could probably go down to 3.1 and see no change in quality
  • I think for the resolutions above that, 4.1 is good
• Pick a higher min qp value
  • They have their min set to 8, have they tried going up to 15 to see if this is better balance of quality and efficiency?
  • I am saying 15 as an arbitrary value, but trialing different QPs could lead to lower bitrates. They need to find the values that fit their use case.
• Add in background detection to help save bits
  • V4L2_CID_MPEG_VIDEO_BACKGROUND_DETECTION to 1
  • This tool is helpful in cases where inter-frames have common background and qp is lower (if they decide to stay with 8 as their min)
• Lastly, and most importantly, I would tell them to set the VBV_BUFFER_SIZE to the min (10) with using constant bitrate mode
  • V4L2_CID_MPEG_VIDEO_VBV_SIZE to 10
  • The driver defaults to 1000, but this is too much tolerance for the given use case. When I drop this value down for this customers resolution, the bitrate range is significantly smaller and I don’t see any large spikes

This was the final pipeline I used to do my testing in the 10.0 SDK, let me know if you have any comments on it:

gst-launch-1.0 v4l2src device=/dev/video2 io-mode=dmabuf num-buffers=1000 ! queue ! video/x-raw,format=YUY2,width=640,height=480,framerate=30/1 ! ticolorconvert ! video/x-raw, format=NV12, width=640, height=480, framerate=30/1, interlace-mode=progressive, colorimetry=bt601 ! v4l2h265enc extra-controls="enc, video_gop_size=(int)9, frame_level_rate_control_enable=1,video_bitrate=8000000, video_bitrate_mode=1,vbv_buffer_size=10,prepend_sps_and_pps_to_idr=1,hevc_strong_intra_smoothing=1,hevc_minimum_qp_value=8,hevc_maximum_qp_value=51,hevc_max_num_of_candidate_mvs=2, hevc_constant_intra_prediction=1,generate_access_unit_delimiters=0,hevc_tmv_prediction=1,background_detection=1" ! video/x-h265,level='(string)4.1' ! h265parse ! mp4mux ! filesink location=bg_cbr.mp4

Hope this helps.

Best Regards,

Suren

Hi,Suren,

    This commit is about the update of the decoder,we only use encode for am62p. So this may not solve out problem.

Best Regards,

Qinghong