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It probably has nothing to do with the resolution, but everything with the audio codec. My guess is that those 720p channels include a DTS or AC3 multichannel audio track, and you are letting the Pi decode and downmix that. Thats when it struggles. 720p shouldnt be a problem when using audio passthrough, assuming you purchased and installed the mpeg2 codec which those streams most likely use.
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Lucky you. 99% of the channels here are 2 channel PCM :/
Anyway, Ive not had trouble with 5.1 AC3 decoding myself yet, but I have read it can stretch what the Pi is capable off. Perhaps only in combination with mpeg2 (rather than x264 which I use almost always) ?
In this cause though, I guess its more likely the 1080i recordings have a AC3 track or less, and the 720p recs a DTS track. And that would cause stuttering on a Pi when not passing through.
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Thanks for what seems to be a very informative thread.
I'm new to XBMC , relatively new to the Raspberry pi, and only moderately experienced with Unix/Linux, but not with A/V topics, so I really don't know what I'm doing.
I recently installed XBMC on my Raspberry pi. I first put it on an SD card with Arch Linux. I then put it on an SD card that I recently installed the Wheezy system. XBMC seemed to install OK on both systems (although it was an effort on Arch Linux), and I was able to run it, however when I tried to play an MPEG4 video file, the AC3 audio played fine through the HDMI output, but I didn't get video. It was the same on both systems. All I got was a small thumbprint of the video down at the bottom right, which was frozen on the first frame of the video.
Previous to trying XBMC, I had tried playing the same file with both VLC and mplayer2. Mplayer 2 played the video at about 1/30 normal speed, and didn't play any audio, VLC just refused to play anything.
I was starting to think that the RPi just wasn't capable of playing medium bitrate HD (it was a 12.5 Mbps H264 video recorded off a PBS sat feed), however after reading this thread, it sounds like it should be able to play the video, so I must be doing something wrong.
I've read that the RPi has hardware acceleration for MPEG4, but I'm wondering if something has to be done to enable it?
I have the OS on a class 10 SD card that is supposed to be capable of 20 MBps, although when transferring the OS to the card, it seemed to be only going at about 6 or 7 MBps. So I thought that perhaps I would put the video file on a USB thumbdrive, but that didn't help. I know that MPEG2 hardware acceleration isn't enabled without a fee, but I tried a similar mpeg2 file, and it behaved in a similar manner, which made me think that the problem must be that the MPEG4 acceleration isn't enabled, but I have no idea of how to tell if that's the case or not.
Is there something that needs to be done to enable mpeg4 acceleration? Or any other thing I've omitted that would cause my problems?
Thanks in advance.
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@ wejones being a Linux newbie your best bet would be to install an XBMC distro be it Raspbmc, OpenElect or Xbian. Personally I use Raspbmc. I don't want to start another "distro war" here, try them all and see which one fits your needs. The xbmc debs for the regular Linux desktop distros will never match the performance of a system that is tuned to run XBMC
If I have been of help, please add to my reputation as a way of saying thanks, it's free.
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Thanks. I did try to download one of those, I think it was the Raspbmc, however what downloaded was only a stripped down loader version that tried to go on the internet to get the rest. Problem is, I have limited internet bandwidth, and for big files, I take my laptop to a nearby town where they have free wireless, and I can't take the RPi, so I need a full image. I will look harder though, and at the other two mentioned above.
Can I ask just how high a bitrate the RPi can play with XBMC, both via MPEG4 and MPEG2 with the license enabled? Most of the video I play is that 12.5 Mbps MPEG4, but I also occasionally play video that's over twice that.
Also, the RPi I have was given to me as a gift, and it is not the newest one with additional RAM. I've ordered one of the newer ones, and I'm curious if the additional ram might help with the issues I observed. Also, can I assume from the above that with XBMC there isn't anything I need to do to enable the hardware acceleration?
Thanks.