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VBR and CVBR

Kowin Hsieh
Intellectual 345 points

Hi 

How can I verify if the stream is VBR or CVBR (H.264)???

thanks

 

 

  • 0
    TI__Genius 17215 points

    Hi,

    There are no headers which tells this behaviour, One has to analyze the stream to check if the desired RC is working fine or not. Under which platform context is this being disucssed ? What is your understanding diff of VBR and CVBR ?

    regards

    Yashwant

  • 0 in reply to Yashwant Dutt
    Intellectual 345 points

    Hi Yashwant

         Can you instruct me how to analyze the stream to know the RC is VBR or CVBR? (I usually use streameye to analyze the stream)

         My platform is DM36x with Linux OS, basically the IPNC.

         My understanding the diff of VBR and CVBR is that they are basically the same but the CVBR have a contraint MAXBitrate??? Is that correct???

         regards,

     Kowin  

  • 0 in reply to Kowin Hsieh
    TI__Prodigy 635 points

    Hi Kowin,

    Hope this link should be helpful,

    http://processors.wiki.ti.com/index.php/DM36x_Rate_Control_Modes

    Please let us know if you want more details.

    Rgds, mahant

     

  • 0 in reply to Mahant S
    Intellectual 345 points

    Hi mahant

         Thanks. I have read this wiki before.

         But I don't know how to verify if the current RC is VBR or CVBR. they are too similar.

         How to define the normal complexity and higher complexity???

         How can you verify the VBR and CVBR? I mean how can I test it???

         Thanks again

    best regards,

    Kowin

     

     

     

       

  • 0 in reply to Kowin Hsieh
    TI__Prodigy 635 points

    Hi Kowin,

    First of all, CVBR is recommended for video surveillance applications. So explaining Normal complexity in such scenarios, it will be the time where there is not much activity or a static sequence with very less motion between frames. High complexity is the duration where there is relatively higher motion between frames.

    To test this on standalone one thing you can try is to interleave a high motion sequence between a static sequence. For example after 300 frames of static sequence insert 100 or so frames of high motion sequence and follow up it with static sequence. 

    Encode it with VBR and CVBR. Observe the bits consumed on frame by frame basis. You can observe the pattern as shown in,

    http://processors.wiki.ti.com/index.php/H.264_DM36x_Ver_2.0_Codec#CVBR_Rate_control

    Under CBVR  section. But in case of VBR the bits distribution will be averaged out.

    In case you are using IPNC, start by encoding static data and eventually(after some seconds) follow it up some motion. Taking a bitstream dump, you should be able to observe the bit distribution pattern as explained above with CVBR.

    Rgds, mahant

  • 0 in reply to Mahant S
    Intellectual 345 points

    Hi mahant

         Thanks you very much. I will try to test it! thanks again.

     

    best regards,

    Kowin

  • 0 in reply to Kowin Hsieh
    Expert 2790 points

    Hi I want to operate DM365 MPEG4 Encoder (dm365_mpeg4enc_01_10_00_03_production.bin) in VBR mode. In order to get a linear variation in bitrate I set the parameters as follows. rateControlPreset=IMP4VENC_CVBR_LBR1; and to control the quality , I set the parameters as follows. rcQMax=31; rcQMin is varied between 4 to 31 (In 20 steps) initQ=0; intraFrameQP=0; interFrameQP=0; I get a variation in bitrate , but is not linear with the degaradation in qualitIy. I have no problems with CBR mode. (I have tried other modes also,IVIDEO_STORAGE & IMP4VENC_CVBR_LBR1), but was not successful. Is this a bug? I have tried with earlier version of the Encoder (which also runs in MJCP). Pls help Regards JK