[mythtv-users] hdhr file troubles on atv2

Raymond Wagner raymond at wagnerrp.com
Tue Feb 15 17:52:11 UTC 2011


On 2/15/2011 11:23, belcampo wrote:
> belcampo wrote:
>> belcampo wrote:
>>> Raymond Wagner wrote:
>>>> On 2/14/2011 09:51, David Evans wrote:
>>>>> I picked up a atv2 about a week ago and I have been tinkering with it.
>>>>>    I have xbmc running on it and using the built in myth:// protocol I
>>>>> can play SD files without any trouble.  The issue that I am having is
>>>>> with files produced by the hdhr.  They will load up but I get a severe
>>>>> stutter with the audio and they are unwatchable.  I tried loading the
>>>>> files via a smb mount and I get constant buffering.
>>>>>
>>>>> I figured the solution would be to transcode the files down to a mpeg4
>>>>> format that should be easier for the ATV2 to play but I'm struggling
>>>>> with the settings of mythtranscode to get a file that plays cleanly.
>>>>> If I could get any insight it would be great.
>>>> The ATV2 does not support hardware acceleration of the MPEG2 output by a
>>>> digital tuner, nor the HD MPEG4 output by mythtranscode.  That means you
>>>> are relying on the woefully inadequate 1GHz ARM for software decoding.
>>>> Until XBMC has fully explored the VideoToolBox API and documented what
>>>> the device is actually capable of, rather than what Apple has restricted
>>>> the device to, the only authoritative reference on the decoding
>>>> performance of that device is on the Apple site.
>>> I do have one for 2 weeks and it can play BluRay as input-format.
>>> I use makemkv to get the BD in a matroska container which I then serve
>>> with minidlna to upnp to XBMC on the atv2, although it scales it down to
>>> 720p, but further it works very well.
>> Sorry I was too hasty, I had encoded them to 1080p but at a lower
>> bitrate with ffmpeg -crf 24, which resulted in visibly perfect,
>> according to mediainfo:
>> Overall bit rate                 : 6 143 Kbps
> Again too fast, I used -cqp 24
> instead of -crf 24

In case anyone wants to follow suit, a quantizer of 18 is considered 
effectively lossless, and 20 or under good enough that most people will 
not notice any artifacts on a moving image, only stills.  A quantizer of 
24 is considered 'medium quality' and will result in artifacts and 
blurring visible by most people even during playback.  There is good 
reason why Bluray video typically runs at upwards of 30Mbps, rather than 6.


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