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Constant Rate Factor to limit transcoding


cochize1
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cochize1

I am trying to fight with transcoding if not neccesary whenever possible. Since the default playback is always set to auto and this causes the transcoding for most of regular 2 GB movie/series files I was wondering what part does CRF plays in all of this?

 

By choosing from 0 to 51, does lower value gives higher bitrate and higher value gives lower bitrate? Is that how it works? Can I adjust the 2.9 Mbps lower or higher in example below by adjusting CRF?

 

5e1126a1ad762_embystreamingmoviehowdecod

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pwhodges

There appear to be situations in which the "auto" setting causes unnecessary transcoding.  It is worth trying setting a speed limit in your client which is greater than that required by any of your files (though not more than your network can handle, of course), because you may well find that this results in less or no transcoding.  

 

Of course, there may still be transcoding for reasons other than bandwidth, such as format incompatibility or subtitle embedding.

 

I wouldn't play with CRF in that way - it controls "quality", not actual bit rate.  And I've recently seen a remark that it's not even used if you have hardware encoding enabled.

 

Paul

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cochize1

Thanks Paul,

I can accept that there is a reason fpr transcoding if there is a format, subtitles, container, audio or any other issue. But in most of the cases the reason is "media bitrate exceeds limit" even though 95% of my files are regular 720p or 1080p mkv or mp4 files and I have fairly good fibre network and also my users do have good internet connections. I already asked some of them to set from auto to 4-10 Mbps and it works most of the time until they connect from other browser or clear their cache files and then I have to ask them again which is quite annoying. And since there is no setting to do this per user from my dashboard I want to find the right settings.

 

As suggested I will leave CRF to it's default 23 value. And by setting a speed limit do you mean 'internet streaming bitrate limit' in Network section of my dashboard? if so is 15 Mbps ok?

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pwhodges

The admin can set the speed limit per user as well as at the server and device levels - this would save having to suggest anything to the individuals concerned.  I've not tried this, so I'm not sure it would have the desired effect, but I don't see why it wouldn't.

 

In the long run, of course, it would be desirable for the unintuitive behaviour of the "auto" speed setting to be improved.

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My experience, don't use auto on the client, set a high limit. My Shield is set to max 80Mbit bitrate on ethernet to fix this issue and now most media direct plays

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cochize1

I don't have a problem watching with direct play in my local network as I can set all my devices to whatever bitrate I want. The problem is when 20+ of my users (friends and family) watch remotly from different devices and locations. I need to ask them to adjust the quality on their end as it is not possible to do that from the dashboard so whomever plays any video from the new location or browser, it is set to auto by default forcing transcoding (regardless internet quality) and I have no control over that.

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My experience, don't use auto on the client, set a high limit. My Shield is set to max 80Mbit bitrate on ethernet to fix this issue and now most media direct plays

 

Hi.  If you are on your local network, the auto setting is already going to do that (in fact, you lowered what it will be :)).

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Hi.  If you are on your local network, the auto setting is already going to do that (in fact, you lowered what it will be :)).

 

I'm not local to the server, nobody is, it's a remote dedi server. My Shield transcodes sometimes on auto where it has no problem with 70Mbit bitrate 4k when I don't use auto

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I'm not local to the server, nobody is, it's a remote dedi server. My Shield transcodes sometimes on auto where it has no problem with 70Mbit bitrate 4k when I don't use auto

 

Okay, you said "on ethernet" so I thought you meant locally.

 

Thanks.

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When you specify the in-app quality setting, that is just a maximum, and the actual transcoded result may at times be less than that. Lowering the crf may help increase the bitrate to be closer to the maximum requested, although it comes with a cost that is explained in the help text for the option.

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