# Bitrate mode setting

**URL:** <https://community.wowza.com/t/bitrate-mode-setting/684>\
**Category:** Wowza Streaming Engine\
**Created:** [May 2, 2013, 2:39pm UTC](https://community.wowza.com/t/bitrate-mode-setting/684 "2013-05-02T14:39:02Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![system](https://sea2.discourse-cdn.com/flex002/user_avatar/community.wowza.com/system/32/447_2.png) [@system](https://community.wowza.com/u/system)\
**Post date:** [May 2, 2013, 2:39pm UTC](https://community.wowza.com/t/bitrate-mode-setting/684/1 "2013-05-02T14:39:02Z")

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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

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**Author:** ![Gustavo\_Villegas](https://avatars.discourse-cdn.com/v4/letter/g/57b2e6/32.png) [@Gustavo\_Villegas](https://community.wowza.com/u/Gustavo_Villegas)\
**Post date:** [May 6, 2013, 11:34am UTC](https://community.wowza.com/t/bitrate-mode-setting/684/2 "2013-05-06T11:34:28Z")

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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

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**Author:** ![Richard\_Lanham](https://avatars.discourse-cdn.com/v4/letter/r/c68b51/32.png) [@Richard\_Lanham](https://community.wowza.com/u/Richard_Lanham)\
**Post date:** [May 6, 2013, 5:24pm UTC](https://community.wowza.com/t/bitrate-mode-setting/684/3 "2013-05-06T17:24:09Z")

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Take a look at these Transcoder encoder params:

[https://www.wowza.com/docs/how-to-control-transcoded-video-with-video-encoding-parameters](https://www.wowza.com/docs/how-to-control-transcoded-video-with-video-encoding-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

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**Author:** ![Gustavo\_Villegas](https://avatars.discourse-cdn.com/v4/letter/g/57b2e6/32.png) [@Gustavo\_Villegas](https://community.wowza.com/u/Gustavo_Villegas)\
**Post date:** [May 6, 2013, 1:28pm UTC](https://community.wowza.com/t/bitrate-mode-setting/684/4 "2013-05-06T13:28:34Z")

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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?

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**Author:** ![1111](https://avatars.discourse-cdn.com/v4/letter/1/71e660/32.png) [@1111](https://community.wowza.com/u/1111)\
**Post date:** [October 7, 2016, 8:02pm UTC](https://community.wowza.com/t/bitrate-mode-setting/684/5 "2016-10-07T20:02:13Z")

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> 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](https://brokenpipe.wordpress.com/2016/10/06/enabling-constant-bitrate-encoding-in-wowza-transcoder/).