Search This Blog

Loading...

04 August 2011

SDHC Card performance

I've been recording a few 1080p videos with a Panasonic Lumix GH1 camera, using a Transcend 32 GB Class 6 card. Lately, the camera started reporting errors, complaining about the card being too slow. I also experienced a few write errors on the camera, which resulted in the camera reporting that the card is faulty. Formatting the card did not help. To make sure that the camera is not at fault, I tested with a Sandisk Class 4 card. As expected, there were no issues with the Sandisk card and it was fast enough to record video.

I decided to perform some more thorough testing on the Transcend card using a Linux system. I decided to examine the sequential write performance of the entire card. For this, I started KDE System Monitor and configured it to plot the read and write speeds on the device. I then used dd to write zeros to the entire card, using sequential writes in 4MB blocks. I also repeated the test with 4kB blocks. Given that this type of test bypasses any filesystem fragmentation issues, a Class 6 card must never write slower than 6MB/s - on any part of the media. As you can see from the attached screen shots, the card performed to specification only in certain areas. There are a number of occasions where the write performance is well below the requirement of a Classs 6 device.

Interestingly enough, the areas of poor performance do not appear in exactly the same locations between tests and also do not seem to be of the same size. I have no definitive explanation for this, but I guess it could be due to something like a wear levelling algorithm being applied, or perhaps bad block re-mapping. Then again, it could be some other issue that's more intermittent and the slowdown is a result of multiple retries and error detection and correction algorithms doing their work. I guess the manufacturer will have means of pinpointing the issue more accurately, but it's unlikely that they would report the root cause back to the end users. Still, it would be educational to find out what goes wrong in memory cards.

Transcend offer a Lifetime Warranty on their cards, so I will contact their technical support to request a replacement. I've tried to use their on-line RMA form, but it seems that this is only available to customers in USA. We'll see how well Transcend looks after their Australian customers - I'm about to contact their technical support in Taiwan.

Transcend 32GB Class 6 SDHC write performance - sequential 4MB writes.


Transcend 32GB Class 6 SDHC write performance - sequential 4kB writes.

15 September 2009

puppy is an old dog now

I have long ago upgraded from a Topfield PVR to a Beyonwiz PVR, so puppy has not really been getting any attention for a few years. It's an old dog now and I won't be teaching it any new tricks.

Since puppy was developed, Linux USB support has improved tremendously. As the Linux kernel matured, advances were made in the APIs that the kernel presents to user space. The supporting user space libraries have also evolved in the last five years. Current Linux kernel supports USB3 - well before Windows or OSX. Such improvements have lead to some APIs, such as usbfs, being deprecated.

The main objective behind developing puppy was to create a utility that could be used in embedded Linux devices. Almost all such embedded devices still run older Linux kernels, so I will not be upgrading the puppy code to switch from the now deprecated usbfs implementation to the new sysfs API. I don't really have the means to test the changes. Current Linux kernels still have support for usbfs, you just need to turn it on.

To bring back the /proc/bus/usb/ entries, rebuild your kernel with CONFIG_USB_DEVICEFS enabled and
mount -t usbfs none /proc/bus/usb

That's all you should need to make your system compatible with puppy.

A third party patch to add sysfs support to puppy is available here. There is no matching patch for ftpd-topfield, however the above recipe should get ftpd-topfield working again.

10 April 2008

puppy 1.14 released

A new release to implement a few requests from users. In particular, support for Ubuntu and for the USB accelerator firmware patch.

Since I no longer use a Topfield PVR, the changes in this release have not been tested. The changes are fairly simple, so I don't expect problems.

10 August 2007

Artbox becomes Final Cut Server

As I posted in December last year, Apple have bought Proximity. The acquisition included a product named Artbox, which is one of the projects I worked on at Proximity. I have written most of the user interface for Artbox.

Apple are about to start shipping a new product called Final Cut Server, which is based on Artbox. There have been many changes under the hood, including a move to Apple's Compressor for transcoding, however the user interface appears to be substantially the same.

06 December 2006

Proximity technology acquired by Apple.

Proximity Emmy
A short blurb on the Proximity web page says that "all Proximity technology and intellectual property was recently acquired by Apple." I used to work for Proximity until the company started experiencing cash flow issues. I certainly hope that the Apple involvement is a way to inject resources into the excellent work that was being done at Proximity. The development team we had at Proximity here in Sydney was a very talented bunch and work was very enjoyable. Proximity was the first (and possibly remains the only) Australian company to win an Emmy award.

This is not the first time that something like this has happened. Back in the 1990's I worked on embedding video streaming technology and building two way interactive systems, including VOD. The company that was originally involved in the R&D of these technologies run out of money (due to law suits on an unrelated project) and the technology ended up being acquired through a string of takeovers by Real Networks. These days, the technology I developed for embedding video content is everywhere. Unlike the guys at You Tube, I didn't get filthy rich.

Perhaps I should have patented all the work I have done - even 0.1% of a few hundred million dollars here and there would come in handy!

20 November 2006

The avatar

Monkey in onsen
I've been using the same avatar for many years now. A few times people have asked about it's origin. The avatar is a cropped part of the picture on the right.

The monkey is a snow macaque in an onsen at Jigokudani, near Nagano, Japan. For those of you familiar with the movie Baraka, these are the same group of monkeys that are depicted at the beginning of Baraka, dozing in the hot spring bath.

I took the picture in 1999, while living in Japan.