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chromecast transcoding


KRA
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I got a Chromecast last week and have been testing it to maybe take the job as a media player in the living room. First thing I notice is transcoding was needed for most my media, a bummer, but not a big deal. However I've had mixed results.

 

My server is a 3.2ghz xeon sandy bridge WHS2011. I did a test and cpu use on the 4 cores are 80-90%, ~50%, ~40%, ~30% - total about 50% when transcoding. But the result is not very good, picture quality is ok, but video is not smooth. Now I know it's a issue with Chromecast only doing 60hz but it's not that.

 

So, since my Freenas has plex as plugin I did a test there, it's also transcoding, cpu use is about the same (same cpu), but quality and smoothness is excellent, very close to original. As far as I can tell it's as good as the original and only the judder from not running native hz a issue. 

 

My MB3 transcoding is set to Max Quality. Is it possible to tweak transcoding ? I've tried several different bitrate settings in the app for chromecast but videosmoothness is allways the same (not smooth) only picture quality is different. 

Edited by KRA
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That's good news, because although first impression on plex was very good, I really don't want to go down that path now. 

 

So should I hold my breath waiting for the improvements ;)  Or should I use plex while waiting ?

 

Also would it possible to add ability to use custom commandline transcode options ?

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danswan

There's a release due in the next week or so that addresses some transcoding issues

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Ghostm

Not to hijack but one thing i am noticing is i get multichannel audio from plex on chromecast, with mbs i only seem to get 2.1.

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Ghostm

I also cant say i notice a picture quality difference, i think it depends on what bitrate settings, and possibly what your server transcoding quality is set at (and you said yours is at max), As far as smoothness i actually notice a bit more stuttering/judder with plex for some material, maybe its due to having your transcoding quality set to max and not being able to keep up? Or maybe its similar to my issue below.

 

I actually give the edge to mbs for picture quality, seems to have less macroblocking, if you have different settings in plex and mbs though you will get different results.

 

My issue is vc-1 content, im picky and i collect full blurays in mkv format, h.264 in my limited testing plays fine. Its vc-1 on chromecast i have issues with. In plex they play fine on chromecast, in mbs they stutter like crazy.

 

I checked cpu usage and plex naturally on high bitrate difficult vc-1 content was using 88% cpu, mbs meanwhile was using about 69%, not sure if theirs anyway to make mbs use more cpu if necessary, but it would be nice if it pushed my system to make sure playback was smooth.

I will have to test mpeg 2 content later.

Edited by Ghostm
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Actually I've tried several different bitrate setting, and the result is allways the same. Picture quality differs, but the same "not smooth" issue remains. I've tried different filetypes, same issue. 

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Ghostm

If you need them from me to can  provide them, but im pretty sure its not pushing my system enough to transcode the vc-1 high bitrate material fast enough.

 

Will provide logs later, also want to try mpeg-2 material. 

Edited by Ghostm
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Tikuf

Vc-i decoding is single threaded as far as I am aware so it cannot be pushed any further (I could be wrong as it may have changed but I cannot see anything in the ffmpeg code or release notes)

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Ghostm

Here is a debug

 

http://pastebin.com/MBP3WVU2

 

And ffmpeg

 

http://pastebin.com/ZuVy1cbp

 

This is 300 vc-1 bluray file in mkv format, plays fine on plex transcoded to chromecast,plex pushes my system alot more, cpu alot higher, but i get smooth playback.

 

Mb3 constant stuttering 10 seconds in.

 

Hopefully thats not to much info, but i dont want to leave anything out that may help.

Edited by Ghostm
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Ghostm

I will try tonight tikuf, but oddly transcoded to the android client the movie 300 plays fine.

 

Its chromecast it struggles on.

I noticed for both plex and mb3 sending to chromecast requires more cpu usage, but while plex takes my cpu to 88-90 to ensure smooth vc-1 playback on chromecast, ffmpeg wont push it past 69.

So i am wondering if this is a chromecast issue.

 

Both bitrates in android are set to 6mbps, and 6mbps for chromecast.

 

Last night i played 300 on the android client and got no stuttering, using the same bitrate on chromecast, as soon as i pushed it to chromecast, it was freezing non stop.

Edited by Ghostm
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Tikuf

Ah ok it is due to the server still using 2 threads for webm (most likely)

 

default droid is hls which is h264/aac

chromecast is webm vpx/vorbis

 

so not apples to apples

 

What cpu are you running?

I will wait for some logs but it is likely your cpu is not quite able to do webm in 2 threads atm. If you drop the bitrate you may see slightly faster conversion speeds (depending on source material).

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Ghostm

I see, my desktop cpu is a bit older its a 3.2ghz, amd tripple core, but i just find it strange plex can play it fine, does plex do something different? It just seems to push my cpu usage alot more and thus i get smooth playback of vc-1 material on chromecast.

 

Last night i seen plex crank up my cpu at 93% at one point but it was smooth.

Edited by Ghostm
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Tikuf

Plex use mp4 dash we currently use webm. Dash will come online soon just have some kinks to iron out so that it works and plays nicely with others.

 

Webm will improve prob next server build although it may not make much diff  to a tripple core.

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Ghostm

I see thanks for the info.

 

Mpeg-2 plays relatively fine as well, so its just the vc-1 stuff for me.

 

One other thing on plex i get multichannel audio on chromecast, with mbs i only seem to get 2.1?

As for the judder, just testing my mpeg2 bluray (kingdom of heaven) they both had a bit of judder that i noticed, i probably have not compared as much as the op has, so i cant say for sure, i will let him discuss that with you.

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Plex use mp4 dash we currently use webm. Dash will come online soon just have some kinks to iron out so that it works and plays nicely with others.

 

Webm will improve prob next server build although it may not make much diff  to a tripple core.

 

I can provide logs later, but please tell are these webm improvements in current dev server ? 

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Tikuf

I can provide logs later, but please tell are these webm improvements in current dev server ? 

You should see improvement in the next build. 

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I wouldn't worry about it for now. We'll get an update into the android and ios releases to stream it differently, which is going to make this comparison moot. They both have bug fix releases coming anytime now.

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