High bit rate (> original)

General discussion about PS3 Media Server (no support or requests)

High bit rate (> original)

Postby sanju » Mon Feb 02, 2009 6:59 am

I am wondering if its problem with my setup..when i press display in PS3 remote, while streaming video from PMS ..i see bit rate to be as high as 100 mbps in so cases although my original video (.vob file) wouldn't be more than 20 mbs. Why does PMS try to transcode the video at more than the original rate..or is it something i am missing in my setup.

Thanks,
sanju.
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Re: High bit rate (> original)

Postby ExSport » Mon Feb 02, 2009 1:05 pm

Every re-encoding is loss of quality. If original bitrate is 10Mbits, you can't re-encode it at 10Mbits with minimal quality loss.
Also you can't expect no quality loss when you recode 10Mbit stream to 500Mbits, so higher bitrate, lower quality loss.
If your network link is not sufficient for high bitrates, use limits for it.
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Re: High bit rate (> original)

Postby kramsy » Mon Feb 02, 2009 7:34 pm

weird... vob files are supported natively by the PS3... it shouldnt be reencoded/transcoded. quality should remain the same.
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Re: High bit rate (> original)

Postby ExSport » Mon Feb 02, 2009 7:39 pm

Read more here in the forum. You can force to not transcoding but you will loose subtitle support...
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Re: High bit rate (> original)

Postby sanju » Tue Feb 03, 2009 9:29 am

In order to get subtitle, re encode is necessary..but my question was something else..if original movie is 20Mbps then there is no point in re-encoding it at higher rate..however in my case i get re-encoded movie at ~100 Mbps..shouldn't this, by default, be done in PMS (to restrict reencode rate < original movie rate).. i can't do this manually in PMS.conf.. since i won't be knowing the original rate movie rate.
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Re: High bit rate (> original)

Postby shagrath » Tue Feb 03, 2009 9:38 am

vob files are not transcoded by default. Are you sure there's no srt files ? and you didn't enter the #transcoded# folder ?
other cause of this "100mbps" display is you simply have some stutters cause your network connection does not support 20 mbps streaming? wireless ?
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Re: High bit rate (> original)

Postby sanju » Tue Feb 03, 2009 10:01 am

Sorry for the confusion..There is .srt file and it says subtitle detected..and then i enter #TRANSCODE# folder..and i watch movie from there. I see 100 Mbps rate in this case.

When i watch without entering into #TRANSCODE# folder then every thing is fine..PS3 shows rate ~8-10 Mbps..i guess this is original movie..which plays nicely..

My question was for #TRANSCODE# folder, since i need to see subtitle ..i enter this folder..which enables transcoding i guess..now in this case i see rate upto 100 Mbps..which i thought was not necessary since original movie itself doesn't go beyond 20 Mbps.
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Re: High bit rate (> original)

Postby ExSport » Tue Feb 03, 2009 12:12 pm

100Mbit is somehow high for 720x480 resoluition so maybe you use Wireless? When network link is capable of 20Mbits and video bitrate is 30Mbit, then you will see not correct bitrates on PS3, e.g. 50-200Mbits because link is poor....but then video will shutter.
But as I said, when you transcode=re-encode at same bitrate as original, quality loss will be greater than when you use 2*bitrate. Because that you can set "compression quality" in PMS regarding your CPU and network link.
Last edited by ExSport on Tue Feb 03, 2009 9:16 pm, edited 1 time in total.
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Re: High bit rate (> original)

Postby sanju » Tue Feb 03, 2009 7:36 pm

Thanks folks for clearing my confusion..i guess, since i use wireless..PS3 is not showing correct rate incase wireless link is not able to cope up with the transcoded rate.
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Re: High bit rate (> original)

Postby Joksi » Wed Feb 04, 2009 4:43 pm

sanju wrote:I am wondering if its problem with my setup..when i press display in PS3 remote, while streaming video from PMS ..i see bit rate to be as high as 100 mbps in so cases although my original video (.vob file) wouldn't be more than 20 mbs. Why does PMS try to transcode the video at more than the original rate..or is it something i am missing in my setup.

Thanks,
sanju.


The easy answer is that your vob probably contains h264 codec (if its HD) and PMS transcodes to a PS3 supported format, mpeg2.
The fact is that you need higher bitrate in mpeg2 to achieve the same thing as with h264. h264 is much more efficient, keeping the high quality.
The problem with h264 is that not many CPUs can handle realtime transcoding of this codec, so mpeg2 is used, and hence the higher bitrate.

So the best thing is to play supported formats (pure streaming) or use tsMuxer for unsupported formats if not needing subtitle support. tsMuxer will only remux, so you will not get a higher bitrate but the original source bitrate.
For subtitles you will have to use transcoding.
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