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Thread: Bitrate mode setting

  1. #1

    Default Bitrate mode setting

    Hi there .... I'm quite new to using transcoding, so, please excuse me for questions that could be already discussed (even though I didn't find the answer for mine here)

    When I transrate, is there a way to tell if I want to use Constant Bitrate or Variable Bitrate? or should I assume that 'cause it's just transrating, it will respect how the source was encoded? What does the Bitrate setting means in case of a Variable Bitrate? ... Average over how many seconds?

    thanks

  2. #2

    Default

    hi there .... sorry for the insistence .... any chance to get an answer?
    I have CBR videos at 5Mbps, when transrated to 1.5 Mbps using Wowza and streamed out by HLS and MPEG-TS, they are VBR

    thanks

  3. #3
    Join Date
    Dec 2007
    Posts
    21,962

    Default

    Take a look at these Transcoder encoder params:
    http://www.wowza.com/forums/showthre...ing-parameters

    You will see output like this:

    INFO server comment - # long: bit rate stuff: H264_CBR, H264_CQT, H264_VBR or H264_TQM
    INFO server comment - mainconcept.bit_rate_mode: 2

    Search for CBR. I only have the above, but look for these 3:

    mainconcept.bit_rate_mode: 0
    mainconcept.bit_rate
    mainconcept.max_bit_rate

    bit_rate and max_bit_rate should probably be the same. I have not experimented with these. Other tests have not been conclusive.

    Richard

  4. #4

    Default

    thanks ... see log below ... as per what you mentioned, I'm set up for CBR, right?

    2013-05-06 21:49:42 GST comment server INFO 200 - # long: bit rate stuff: avg bitrate; if 0, use above quantization parameters

    2013-05-06 21:49:42 GST comment server INFO 200 - mainconcept.bit_rate: 1500000


    2013-05-06 21:49:42 GST comment server INFO 200 - # long: bit rate stuff: H264_CBR, H264_CQT, H264_VBR or H264_TQM - - - 190134.267 - - - - - - - - - - - - - - - - - - - - - - - - -
    2013-05-06 21:49:42 GST comment server INFO 200 - mainconcept.bit_rate_mode: 0 - - - 190134.267 - - - - - - - - - - - - - -

    2013-05-06 21:49:42 GST comment server INFO 200 - # long: bit rate stuff: max bitrate, used in VBR mode - - - 190134.287 - - - - - - - - - - - - - - - - - - - - - - - - -
    2013-05-06 21:49:42 GST comment server INFO 200 - mainconcept.max_bit_rate: 1500000 - - - 190134.287 -



    what can be wrong then as I see my video output being VBR?

  5. #5
    Join Date
    Dec 2014
    Posts
    18

    Default

    Quote Originally Posted by tavius View Post
    what can be wrong then as I see my video output being VBR?
    In addition to the above parameters you also need a fairly low VBV buffer size.
    I had the best results using a single-frame VBV, that is the bufsize = bitrate / framerate. The parameter is mainconcept.bit_rate_buffer_size, see full example here.

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