720p stuttering on 1.83GHz C2D Mac Mini
#1
I'm still seeing some very poor quality playback on my 2007 1GB 1.83GHz C2D Mac Mini, and I'd appreciate it if somebody could help me with an experiment. I'm using a Hauppauge HDPVR to dump video from my DirecTV DVR and I've recorded two clips - one with a very low bitrate (1-2Mbps VBR) and one with a "reasonable" bitrate (7-9Mbps VBR). They're both H.264 MP4 files and have DD5.1 AC3 audio.

The "reasonable" file is at http://files.me.com/rccoleman/cdzeqp.mov
The "low bitrate" file is at http://files.me.com/rccoleman/734za5.mov

Ignore the ".mov" extensions - they're actually ".mp4" files.

Both of these files cause very annoying dropped frames during playback. The worst part is the "zoom into the window across the rooftoop", and I've been using that as my benchmark so far.

Could somebody with an equivalent system try them and let me know if you get dropped frames? Or if there's anything weird about the files?

This is an offshoot of http://forum.xbmc.org/showthread.php?tid=55563, which has some more info about my setup.

Thanks,
Rob
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#2
Please see the sticky about reporting problems in a useful manner. Namely the mediainfo output for the files and a full debug log on pastebin.
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#3
No wonder these files drop frames, they're encoded at 60 fps, I can't even play them without vdpau even though they're only 720p.
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#4
No problem playing them on a 2.4GHz MacBook.

734za5.mov is very low quality, icky Smile

cdzeqp.mov much better quality, I'm running at about 115 percent CPU on this one. A few frame drops seen via OSD but nothing visually.

These are encoded with VBR, I've had better success with CBR under the HDPVR. A ~2Mb rate CBR is playable on the AppleTV with skiploopfilter=8.

I would try 2-3Mb rate CBR and see if you have better luck with that.

"zoom into the window across the rooftop" is a good check, lot's of things going on. With 734za5.mov, the encoder setting is just does not enough to capture the zoom so it looks really bad.

I'll give these a try in a bit on a 1.6GHz CoreDuo MacMini.
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#5
Thanks for the quick responses, guys.

As far as the framerate is concerned, 60fps is pretty standard for 720p, isn't it? In fact, isn't that generally the definition of it? It's the output that I get from my DirecTV DVR, which is where I grabbed this from. The Hauppauge just encodes the input signal in hardware, so I can't change the framerate without re-encoding (ick!).

I tried the CBR recording that Davilla recommended and it was better in terms of dropped frames, but the quality was horrible. The log from that run is here. The file is here. I tried a higher bitrate CBR file last night and there were dropped frames everywhere. Incidentally, when I select "CBR" in HDPVRCapture, MediaInfo is reporting that the resulting file is VBR. I'll have to look into that...

The log from the "normal bit rate" run is here. The log from the "low bit rate" run is here.

I don't get any dropped frames on my 2.8GHz MBP with the "normal" clip, but it has a heck of a lot more horsepower than the mini.

The mediainfo output for the "low bitrate" sample is:
Code:
*** MediaInfo Mac // Plain text file report
2009-08-09 11:20:22 -0700
Information for File: 20090809_024256.m2ts.mp4

General / Container Stream # 1
    Total Video Streams for this File -> 1
    Total Audio Streams for this File -> 1
    Video Codecs Used -> AVC
    Audio Codecs Used -> ac-3
    File Format -> MPEG-4
    Play Time -> 1mn 30s
    Total File Size -> 13.2 MiB
    Total Stream BitRate -> 1 232 Kbps
    SubTitle (Tag) -> Created with HDPVRCapture
    Encoded with -> Lavf52.30.1
Video Stream # 1
    Codec (Human Name) -> AVC
    Codec (FourCC) -> avc1
    Codec Profile -> [email protected]
    Frame Width -> 1 280 pixels
    Frame Height -> 720 pixels
    Frame Rate -> 59.940 fps
    Total Frames -> 5406
    Display Aspect Ratio -> 16/9
    Scan Type -> Progressive
    Colorimetry -> 4:2:0
    Codec Settings (Summary) -> CABAC / 4 Ref Frames
    QF (like Gordian Knot) -> 0.015
    Codec Settings (CABAC) -> Yes
    Video Stream Length -> 1mn 30s 190ms
    Video Stream BitRate -> 833 Kbps
    Video Stream BitRate Mode -> VBR
    Bit Depth -> 24 bits
    Video Stream Size -> 8.96 MiB (68%)
    Date of Original Encoding -> UTC 2009-04-04 16:00:00
Audio Stream # 1
    Codec -> AC-3
    Codec (FourCC) -> ac-3
    Audio Stream Length -> 1mn 30s 208ms
    Audio Stream BitRate -> 385 Kbps
    Audio Stream BitRate Mode -> VBR
    Number of Audio Channels -> 2
    Sampling Rate -> 48.0 KHz
    Bit Depth -> 16 bits
    Audio Stream Size -> 4.14 MiB (31%)
    Date of Original Encoding -> UTC 2009-04-04 16:00:00

Reasonable VBR bitrate:

Code:
*** MediaInfo Mac // Plain text file report
2009-08-09 11:21:10 -0700
Information for File: 20090809_023646.m2ts.mp4

General / Container Stream # 1
    Total Video Streams for this File -> 1
    Total Audio Streams for this File -> 1
    Video Codecs Used -> AVC
    Audio Codecs Used -> ac-3
    File Format -> MPEG-4
    Play Time -> 1mn 37s
    Total File Size -> 84.7 MiB
    Total Stream BitRate -> 7 272 Kbps
    SubTitle (Tag) -> Created with HDPVRCapture
    Encoded with -> Lavf52.30.1
    Encoding Library -> Apple QuickTime
Video Stream # 1
    Codec (Human Name) -> AVC
    Codec (FourCC) -> avc1
    Codec Profile -> [email protected]
    Frame Width -> 1 280 pixels
    Frame Height -> 720 pixels
    Frame Rate -> 59.940 fps
    Total Frames -> 5853
    Display Aspect Ratio -> 16/9
    Scan Type -> Progressive
    Colorimetry -> 4:2:0
    Codec Settings (Summary) -> CABAC / 4 Ref Frames
    QF (like Gordian Knot) -> 0.124
    Codec Settings (CABAC) -> Yes
    Video Stream Length -> 1mn 37s 647ms
    Video Stream BitRate -> 6 876 Kbps
    Video Stream BitRate Mode -> VBR
    Bit Depth -> 24 bits
    Video Stream Size -> 80.0 MiB (95%)
    Date of Original Encoding -> UTC 2009-04-04 16:00:00
Audio Stream # 1
    Codec -> AC-3
    Codec (FourCC) -> ac-3
    Audio Stream Length -> 1mn 37s 664ms
    Audio Stream BitRate -> 387 Kbps
    Audio Stream BitRate Mode -> VBR
    Number of Audio Channels -> 6
    Sampling Rate -> 48.0 KHz
    Bit Depth -> 16 bits
    Audio Stream Size -> 4.51 MiB (5%)
    Date of Original Encoding -> UTC 2009-04-04 16:00:00

CBR 2-3Mbps (CBR selected in HDPVRCapture, at least. I'm not sure why it's saying VBR below):

Code:
*** MediaInfo Mac // Plain text file report
2009-08-09 12:06:14 -0700
Information for File: 20090809_120237.m2ts.mp4

General / Container Stream # 1
    Total Video Streams for this File -> 1
    Total Audio Streams for this File -> 1
    Video Codecs Used -> AVC
    Audio Codecs Used -> ac-3
    File Format -> MPEG-4
    Play Time -> 1mn 25s
    Total File Size -> 30.4 MiB
    Total Stream BitRate -> 2 994 Kbps
    SubTitle (Tag) -> Created with HDPVRCapture
    Encoded with -> Lavf52.30.1
Video Stream # 1
    Codec (Human Name) -> AVC
    Codec (FourCC) -> avc1
    Codec Profile -> [email protected]
    Frame Width -> 1 280 pixels
    Frame Height -> 720 pixels
    Frame Rate -> 59.940 fps
    Total Frames -> 5108
    Display Aspect Ratio -> 16/9
    Scan Type -> Progressive
    Colorimetry -> 4:2:0
    Codec Settings (Summary) -> CABAC / 4 Ref Frames
    QF (like Gordian Knot) -> 0.047
    Codec Settings (CABAC) -> Yes
    Video Stream Length -> 1mn 25s 218ms
    Video Stream BitRate -> 2 598 Kbps
    Video Stream BitRate Mode -> VBR
    Bit Depth -> 24 bits
    Video Stream Size -> 26.4 MiB (87%)
    Date of Original Encoding -> UTC 2009-04-04 16:00:00
Audio Stream # 1
    Codec -> AC-3
    Codec (FourCC) -> ac-3
    Audio Stream Length -> 1mn 25s 216ms
    Audio Stream BitRate -> 384 Kbps
    Audio Stream BitRate Mode -> VBR
    Number of Audio Channels -> 2
    Sampling Rate -> 48.0 KHz
    Bit Depth -> 16 bits
    Audio Stream Size -> 3.90 MiB (13%)
    Date of Original Encoding -> UTC 2009-04-04 16:00:00
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#6
mmmfishies Wrote:Thanks for the quick responses, guys.

As far as the framerate is concerned, 60fps is pretty standard for 720p, isn't it? In fact, isn't that generally the definition of it? It's the output that I get from my DirecTV DVR, which is where I grabbed this from. The Hauppauge just encodes the input signal in hardware, so I can't change the framerate without re-encoding (ick!).

You don't come across 60 fps all that much, most stuff is 24 fps, this recording is actually a 24 fps movie encoded in a 60 fps video.

Even though this video is a low bitrate one, other parts of the system are stressed at roughly the same load as playing 25 fps 1080p would do.
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#7
Good to know. I'm trying to find a way to archive TV shows and movies from my DVR, which seem, to me, to be either 1080i/30 or 720p/60, I'd like to find a way to deal with it. I've been doing some investigation at my local Apple store, and I've found that a 2GHz mini wasn't up to the 'normal' clip, but a 2.26MHz Macbook did just fine. Maybe I should look into a 2.26GHz mini for my HTPC, unless there's a quick and easy way to turn 720p/60 into 720p/30.
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#8
The only way is encoding it again.
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#9
I'm doubtful of this because of the shear size of the frame, but do you think I'd be better off using 1080i/30?

Thanks for your help,
Rob
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#10
As bobo1on1 is not in the US, I'll illuminate him Smile

US is the land of 720p60, that stems from one of the digital ATSC format being 720p60. Most all setup-boxes (cable, sat, etc) output 480i/480p/720p/1080i in 30 and 60 hertz. Nothing outputs 720p24. So when one is capturing the digital output, this is the choice you get. Most (including me) choose 720p60 as a capture format.

Now 720p video files found on torrents are typically 24 hertz, not sure how they get this way. So if you are into torrents, 720p24 is what you will find, if you want to record your own content for time shifting purposes (which is perfectly legal under US laws), then 720p60/1080i30 are your HD choices.

1080i30 is interlaced, record this and now you get to play de-interlace games for playback. I prefer 720p60 for this one reason.

EDIT: another thing to think about is if you do get a new MacMini with the nvidia chipset, then you could always run linux and now hardware video content decode using nvidia vdpau is possible.
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#11
davilla Wrote:1080i30 is interlaced, record this and now you get to play de-interlace games for playback. I prefer 720p60 for this one reason.

My reasoning, too. 1080i motion scenes look awful coming from the Mac Mini.

davilla Wrote:EDIT: another thing to think about is if you do get a new MacMini with the nvidia chipset, then you could always run linux and now hardware video content decode using nvidia vdpau is possible.

I'm seriously thinking about this. Perhaps 10.6 will allow access to hardware acceleration.
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#12
mmmfishies Wrote:Perhaps 10.6 will allow access to hardware acceleration.

Don't bet on it, only Apple apps (quicktime player) has access to hardware acceleration under OSX. I'm also an Apple Select Developer Smile
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720p stuttering on 1.83GHz C2D Mac Mini0