taril | # 71 | 2010-07-12, 15:48 | Report

There wont be 720p in N900, ever, there wont be 720p in N900 ever!

dof250 | # 72 | 2010-07-12, 16:14 | Report

I think you could better the the number of IO operations on both with different sizes. Constant throughput is enough for HD but i think its more depended on the number of IO operations it can handle.

Ayodeji | # 73 | 2010-07-12, 16:30 | Report

The camera firmware repository is located here (contains a list of video/image capture modes that are recognized by the camera):

http://gitorious.org/omap3camera/

The specification for the 5 megapixel image sensor is located here (not very useful for encoding, I suppose, but it's a good reference nonetheless):

http://retiisi.dyndns.org/~sakke/foo...APL_090511.doc

I posed the question of video recording in 1280 x 720 to a developer here who did some work with the camera on the N900 (I'm not mentioning his user name specifically, as I'm not sure if he'll receive a multitude of messages posing the same question as a result), and the developer thought that it might be possible at ~20 frames/second or so.

As attila77 mentioned, the 3430 is not advertised as being capable of performing HD encoding, and Samsung very well may have adjusted the encoding bitrate in order to achieve the desired result with the Omnia HD. I happen to own an Omnia i8910 HD, and I also happen to have one of the first videos I recorded here on my hard drive at the moment. The video rate statistics for this 48-second clip are (as reported by Windows):

22 frames/second
8924 kbps data rate (video only)

I don't have an N900 video clip available at the moment, so I'm not sure how the data rate compares, but perhaps this information can be used as part of a feasibility assessment (granted, this is only a single clip)...

ndi | # 74 | 2010-07-12, 16:50 | Report

True, however, with no other apps writing to the cards, raw throughput is a good indication of whether or not the writing speed is a limiting factor for video.

On my older phones, the access speed was so poor that PC-encoded video that went over 3 Mbps even over a short period choked, because that's how much a MMC back then could put out.

I still think N900 has an access issue, likely related to buffers, as some videos still choke without ceiling the CPU. Small chunk writing could be the death of it. IMO, for the camera (writing 400-500K/s), a buffer should be several MB in size and flush in at least 1M segments.

While flash virtually has no seek times, an SD card is far from ideal flash, let alone whatever the recording app tries to write. If it calls flush on the file every 512 bytes it could have an SSD in there, it's still be slow.

Anyway, I posted the figures so other people can compare their speeds and their performance. I'm trying to isolate the most limiting factor.

I'll try to dig out performance through multiple buffer sizes and flushes, however, without knowing what keeps the camera from recording smoothly it makes little difference.

vitamina | # 75 | 2010-07-12, 17:09 | Report

Understand that no one will benefit from enhanced video recording?

ndi | # 76 | 2010-07-12, 17:17 | Report

Why? Better quality, standardized format, more detail.

Higher resolution video has better detail than the lower, because detail is there to begin with.

If you means because the screen on N900 isn't large enough, then so what? My DSLR doesn't have a 10 Mpx screen.

--

I didn't edit my post because they're both quite large.

Observations:
* ATTO's figures are quite close to mine. That is, over decent buffers throughput's what limiting the writes.

* Note that at 400-500K/s average, you need at least 2K buffers on the EMMC and SD. Any lower and it stutters. Once it drops a frame, flushing buffers for at least half a second means you need a peak of 2 M/s to recover otherwise the segment is lost, that means a minimum of 4 K(?)

* I tried both overlapped IO, direct IO, etc. All figures were withing 5% of each other on lower buffers, and identical on higher buffers (4K+)

* Further testing showed that panning isn't the most load on the camera. From 3200 Kbps, it peaked at 3600 when panning. What pushed the thing over was auto-guessing brightness/exposure. Fading up and down when walking into the sun/shade wen over 4000 kbps (500K/s).

* Also, I was able to sync the dropped frames with the bit rate. Every time it dropped, bitrate was trying to push 4000. As a result, I tried to lower the resolution to fine 4:3 (640x480) and while I have better performance it is also choking on 4000+ bitrate.

We may have a software limitation in place?

Here are the performance tests on both storage systems:

Attached Images

  

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Last edited by ndi; 2010-07-12 at 17:20.

te37v | # 77 | 2010-07-12, 17:22 | Report

that's what they said about overclocking

edit:

@maemomatic: I posted in that thread to potentially persuade Nokia to do something, hopefully they will listen.......but I think it is actually better that the members of this community are doing something about this.

@ndi: Sounds like you have detected the problem! We're one step closer! (Or at least you are :P)

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Last edited by te37v; 2010-07-12 at 17:46.

jaimex2 | # 78 | 2010-07-18, 10:40 | Report

Try removing extra decoder support guys, I got a very noticeable performance boost. It's almost perfect for me now.

ankit255 | # 79 | 2010-07-18, 10:50 | Report

The omap 3430 on n900 is capable of 720p encoding :
"IVA™ 2+ (Image Video Audio) accelerator enables multi-standard (MPEG4, WMV9, RealVideo, H263, H264) encode/decode at D1 (720x480 pixels) 30 fps, and up to 720p resolutions"
source:http://focus.ti.com/general/docs/wtb...emplateId=6123

Why this capability wasn't included by default baffles me. Its there on omnia HD with 3440(almost identical SOC)

jaimex2 | # 80 | 2010-07-18, 11:42 | Report

Bleh, back to stuttering.

Short of over clocking my n900 to 1.5 Ghz I'm out of ideas, I'm considering returning it Just too many little things adding up to a lot of disappointment.

Such a great phone completely gimped. Everything in it gives the impression the people responsible spent enough time on each feature with an attitude of "It kinda works, that'll do... next".

What are the chances NITDroid/Meego will redeem the n900?