• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 98 subscribers
  • Views 495 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DM8148 h264 CBR not really constant

Hongfeng Wang
Genius 3925 points

I used to use VBR, but recently due to this problem
http://e2e.ti.com/support/dsp/davinci_digital_media_processors/f/716/t/284890.aspx
I disabled temporal noise reduction, after that the video bit rate increases dramatically at night, when video noise level is high. I set the target bit rate to 3Mbps, but the generated stream went well above 10Mbps. 

So I tried CBR mode, and to my surprise, it has same issue, it's not constant at all!

I also tried ISS_DNF, but that caused frame rate to drop to 20fps from 30.

Did I miss some parameters I need to set?

  • 0
    TI__Genius 11000 points

    Firstly, please move and uograde to v3.5 as there are fixes/upgrades in this version

    For ISS VNF performance, there are some optimization in performance done for this in v3.5

    From your description, it looks like your night scene has more noise coz of which the bitrate is shooting up a lot

    Can you tune the Qp Min and MAX to 4 to 51 in Video_advanced page, this will give more flexibility for Rate Control to fo to lower QP to achieve lower bitrate

    For CBR, you will see some frameskips if there are instantaneous variations in bitrate, RC will skip frame in roder to maintian bitrate, is this the reason you see lower framerate?

    Do you see this both RC : VBR and CBR?


    Also, what other algorithms are you running in the system? is this causin the performance drop?


    Regards,


    Raghu

     

  • 0 in reply to Raghu Kudva
    Genius 3925 points

    thanks for the reply.

    I will try changing QpMin and QpMax first. 

    Upgrading to 3.5 turned out to be not as easy as the transition from 2.8 to 3.2, I will give it another try though.

    Our IPNC application tries to store 30 days of videos in a SSD, when the bitrate skyrockets at night, it reduced the duration of our recording capacity.

    Frame skipping is not desirable for us either.