Understanding Transcode bitrate displayed in Dashboard

[rbjtech 5284]

Hi,

 

In the Dashboard, any transcoding bitrate is shown incorrectly as a dynamic slowly increasing number - in kbps despite the settings being forced on the client to 1,2 4 etc Mbps.

 

Only when you get to the end of the transcode does it display the correct Mbps setting. 

 

 

As an example above - the Android Client is set to 1 Mbit/sec.  Stats for Nerds matches the Dashboard - it shows it as 155Kbps.  It clearly isn't as the quality is fine for 1 Mbit/sec.

 

The transcode log says it's 1 Mbit/sec - so I'm certain it is - but the dashboard is not displaying this.

 

If I get to end of the transcode (at the end of the film if throttling was on, or as soon as the entire transcode has finished if throttling was off) then it shows the correct value - and Stats for Nerds shows this correctly then too.

 

 

I've tried different settings in the trancode settings, but can't get it to display the correct Transcode bitrate.

 

Can you advise how to show the correct bitrate as helps me tune the settings to cater for my remote users when they are transcoding ..

 

Transcode log attached - Thanks.

ffmpeg-transcode-81c28995-4fae-4e51-b10e-27738d3174b6_1.txt

Edited October 13, 2019 by rbjtech

[Luke 42080]

Hi there, why do you feel this is incorrect?

[Guest asrequested]

It definitely low balls it. It's been this way for a long time. If I set the preference to 3Mb/s, it shows 1.7Mb/s. If I set it to 1Mb/s, the dashboard shows 750kb/s. 

[rbjtech 5284]

Hi there, why do you feel this is incorrect?

 

Hi Luke - If I set a bitrate (or a bitrate gets set for me via Auto) then should it not display the bitrate that it is using in FFMPEG ?, instead it shows a dynamically increasing bitrate starting in the 100's of Kb's which is clearly not correct.  So I believe it's incorrect on two fronts - 1) the transcoding bitrate is not dynamic and 2) it's nothing like the true bitrate that is being used.

 

Thanks.

[Luke 42080]

That is the current actual output bitrate. It's variable bitrate encoding (VBR). It will go up and down throughout the video but it will stay under the limit you've configured.

[rbjtech 5284]

ok thanks for replying Luke - and VBR does make a bit more sense.

 

How is it calculating the Kbps ?  It starts at practically zero and slowly ramps up to the overall 'average' across the entire encode ?

 

If so, then depending on the % completion, you will get an artificially low reading, which seems a bit of an odd way to do it ?

Edited October 18, 2019 by rbjtech

[Guest asrequested]

Any chance of an option to change to CBR? I never use variable.

[rbjtech 5284]

Any chance of an option to change to CBR? I never use variable.

 

It is CQ/CRF Doofus - you can see that in the ffmpeg command line in the transcode log - so I'm really not sure what this value is actually showing or trying to show being brutally honest .. 

 

... ffmpeg.exe -loglevel +timing -ss 00:41:24.000 -f matroska -i file:"\\server\Films 2\Alien (1979)\Alien (1979) - 1080p x264 DTS.mkv" -threads 0 -map 0:0 -map 0:1 -sn -c:v:0 libx264 -filter_complex "[0:0]scale=trunc(min(max(iw\,ih*dar)\,1280)/2)*2:trunc(ow/dar/2)*2" -pix_fmt yuv420p -maxrate 3808000 -bufsize 7616000 -preset veryfast -profile:v:0 high -level:v:0 4.1 -crf 23......

 

If it showed 4 Mbps (which it is) then I'd be happy ! 

Edited October 18, 2019 by rbjtech

[Guest asrequested]

So it is isn't variable?!?!

 

Can we get a more complete answer to our question, please? If I set 4Mb/s I want 4Mb/s, not 2.5 - 3Mb/s. I understand that there's probably a disparity between video bitrate and overall bitrate, but we are getting conflicting information. The bitrate setting is probably an overall bitrate and the dashboard is probably showing the video bitrate. If I am correct, it should not be this way.

 

@@softworkz could you please chime in?