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Review: Plextor ConvertX PX-TV402U personal video recorder

By Glenn Mullikin on July 11, 2005 (8:00:00 AM)

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The Plextor ConvertX, even at an early stage in its Linux support cycle, is a legitimate alternative to the Hauppage video capture cards that so many Linux users are using these days. Last March, Plextor announced the availability of a Linux software development kit for two of their personal video recorders: the ConvertX PVR model PX-TV402U and the ConvertX PX-M402U. I chose to evaluate the ConvertX PVR-PX-TV402U product because I wanted to find a suitable piece of hardware to use in a system that functions as a personal video recorder.

Setting up the hardware

My test system included the following:

  • CPU: AMD Duron 950 mhz
  • Motherboard: Biostar M7VKD
  • RAM: 256 MB SDRAM
  • Video Card: GeForce2 MX with S-video TV-out
  • Sound: on-board, VIA-based
  • Hard Drive: 160 GB 7200 RPM Western Digital EIDE dedicated to video capture
  • USB 2.0 PCI card: Belkin Hi-Speed USB 2.0 5-port PCI card
  • Linux kernel used: 2.6.9 and 2.6.11.6 both successfully
  • Linux OS: Debian unstable
  • Video display devices: 13 inch, 19 inch computer monitors and a 27 inch Sharp TV with S-video input

You can download the Linux SDK for PX-M402 and PX-TV402 for free from Plextor's Web site. Once you unzip and extract the tar.gz file, you have several standard source code files, including a Makefile and a README file. I recommend that you first read the README file because it contains important information about what you'll need in order to successfully use this hardware.

You'll also need hotplug, hotplug firmware, and USB support compiled into your kernel.

Performance

The video capture quality was very good, but it depended upon the source signal. If your source signal is poor with static, you can't expect the result to be anything better, and it may even be worse. However, if you have a clear video signal, you should obtain good, clear captures.

On my test system, the CPU and MEM usage (according to the top command) never went above 3% and 2% respectively. The resolution and format appeared to make no difference in the resource usage figures. As you may know, when you try to capture at a resolution of 720x480 using a cheap TV tuner card, you get dropped frames and higher system resource usage. That wasn't the case with the Plextor card. This is a good indicator of its potential in software setups like MythTV, which require the ability to record one show and play back another simultaneously without maxing out the system.

Box
The Plextor ConvertX PVR

Some may wonder if a USB 2.0 port is necessary. I was able to perform captures with a USB 1.1 port, but I sometimes had problems playing back MPEG4-formatted captures with the 1.1 port. These problems weren't present when I used a USB 2.0 port. I never experienced any problems capturing MPEG2-DVD video at 720x480. At certain resolutions and formats, a USB 1.1 port may be sufficient. For some reason, with a USB 1.1 port, I always had to unplug the power and plug it back in on the unit for the system to recognize it and load the drivers. With the USB 2.0 port, I didn't have this problem, and the drivers were loaded at boot time.

Software

The Linux SDK provides a command line program called gorecord that gives a good idea of the unit's capabilities and features. For instance, you can set the format you want to capture in (e.g. MPEG2, MPEG2-DVD, MPEG4, MPEG1 or MJPEG) as well as a wide variety of other preferences. Since the TV402U comes with an integrated TV tuner, you can tell it what channel you want to capture. Or if you want to use the S-Video or composite input, there is a setting for that, too. A full list of options can be seen by typing gorecord --help from the command line.

I found that a bit rate setting of 1500 to 1750 kilobits per second provided suitable video quality for 720x480 MPEG2-DVD captures. Going beyond that didn't appear to make much difference in terms of video quality. Something to keep in mind is that the -bitrate option is for the video bit rate. The audio bit rate will always be 1536 kilobits per second, so to get the total bit rate, you have to add on the 1536.

Even though the gorecord application sports a tremendous amount of flexibility and features that allow you to exploit every aspect of this hardware, Nathan Lutchansky, the author of the Plextor Linux driver, told me in an email, "The gorecord application serves as example code only and does not aim for maximum compatibility or user-friendliness. It also does not perform A/V synchronization, so the audio and video will usually get out-of-sync after 30 to 45 minutes."

The A/V sync mismatch doesn't have to be much in order to make things really ugly. On a few tests, I found that some videos needed only an adjustment of 0.12 seconds from within Xine in order to bring the audio and video back into adjustment. That may not sound like much, but it can be very noticeable on certain types of video. The best remedy for this problem is to record with MythTV, which natively supports the Plextor ConvertX.

Broadcast
A broadcast on MythTV
Recorded
The same broadcast as recorded by the ConvertX

Working with video files

The MJPEG files that gorecord produces are compatible with the MJPEG Tools suite. Although the programs in MJPEG Tools can use software to encode to a DVD video file, the process is very CPU-intensive. No one wants to do this when he has an expensive piece of hardware that's capable of capturing to a compressed format.

FFmpeg and Transcode are capable of working with the MPEG2-DVD and MPEG1 formats that the Plextor ConvertX produces, but I suspect this is only in a software re-encoding type of way.

Conclusion

If you need a piece of hardware to use from within MythTV, you should consider the Plextor ConvertX PX-TV402U. The quality of the recorded video is excellent, and the system resource usage of the unit is extremely low, which means you get excellent performance when using it from within MythTV. The unit is also a welcome possibility for video capture on laptops since very few options currently exist.

Plextor has added life to Linux by offering full software support for the Plextor ConvertX in terms of open source drivers. You just can't beat that. Every piece of hardware that is supported in this way gives users yet another reason to stay with Linux.

Device External PVR
Manufacturer Plextor
OS Support GNU/Linux, Windows 2000/XP
Market Video recording enthusiasts
Price (retail) U.S. $200
Previous version N/A
Product Web site Click here

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Comments

on Review: Plextor ConvertX PX-TV402U personal video recorder

Note: Comments are owned by the poster. We are not responsible for their content.

Boycott Plextor Products!

Posted by: Anonymous Coward on July 11, 2005 08:42 PM
<a href="http://trends.newsforge.com/trends/05/07/05/140214.shtml?tid=152&tid=147&tid=125&tid=132&tid=69" title="newsforge.com">http://trends.newsforge.com/trends/05/07/05/14021<nobr>4<wbr></nobr> .shtml?tid=152&tid=147&tid=125&tid=132&tid=69</a newsforge.com>

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Thanks, but, no thanks.

Posted by: blindcoder on July 11, 2005 09:10 PM
Weren't Plextor the ones threatening legal action against programmers who wanted to give them a larger market by making their products usable under GNU/Linux?

Thanks, but, no thanks. I don't want to do business with a company like that in any way, shape or form.

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Re:Thanks, but, no thanks.

Posted by: Fletch on July 11, 2005 10:25 PM
This is correct. The way to look at this is imagine if the interface for manipulating MythTV looked like a bundled Windows product created by Plextor. So, what would everyone's opinions be seeing Plextor threatening MythTV? Now this isn't the case obviously, as it is hypothetical, but what would be the difference in the two? It is a relative question, becuase this in in fact what they are doing to another project that runs on Linux, when in fact, they are claiming to "embrace" Linux.

J

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The audio is not compressed

Posted by: Anonymous Coward on July 11, 2005 10:24 PM
The reviewer does not comment on the captured file sizes, according to the forums at www.divx.com the developer states that with divx captures it is possible for the audio to be larger than the video!

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Re:The audio is not compressed

Posted by: Anonymous Coward on July 12, 2005 03:18 AM
Actually, these questions are covered in the article, if you read it carefully. There's a paragraph about choosing the optimal bit rate for video quality, which states that the audio is always recorded at the same bit rate. This bit rate exceeds the lowest end of the optimal range for 720x480 resolution video.

It would have been nice, though, if the author had mentioned how big the files actually were after he recorded an hour or half-hour program. Being able to extrapolate is good, but experimental evidence is useful, too.

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Yellow rain

Posted by: Anonymous Coward on July 11, 2005 11:40 PM
Until recently I used, and recommended Plextor DVD burners and products to people.
Since Plextor have recently shown themselves to be two faced about their support for the open source community I will no longer use or recommend their products.
Plextor are wasting their time trying to market this product to us. They are urinating on our backs and telling us it's raining.

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No thanks

Posted by: Anonymous Coward on July 12, 2005 04:58 AM
I use to only buy Plextors... have 3 now but I won't buy them again. Not with the way they treat Linux users. I agree, this is just way two faced.

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v4l-support?

Posted by: Anonymous Coward on July 12, 2005 04:57 AM
Heya,

I was wondering if there is support for the v4l/v4l2-interface for this device?
It seems a nice device, but using the v4l(2) api would make it supported by more applications without any changes to them I suppose. (I don't really know the v4l(2)-api.)

I also think I would prefer a pci(-x)-based-solution. Ofcourse, this box is more portable on the other hand.

Seems nice that they support linux. Don't know what I have to think about them, about their opensource-support.

greetings,

Michel Brabants

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Re:v4l-support?

Posted by: Anonymous Coward on July 16, 2005 10:00 AM
It is a V4L2 and ALSA driver.

Plextor just announced a PCI version but it is available in Japan only.

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Review?!

Posted by: shadestalker on July 12, 2005 11:17 AM
This looks like a total of 20 minutes was spent plugging the device in and running gorecord to see if it worked. A review, it is not.

"but I suspect this is only in a software re-encoding type of way."

At least there's no assertion made here, only a vague admission that nothing was tried except gorecord.

"which means you get excellent performance when using it from within MythTV."

Here's where I must cry foul. Mythtv is mentioned here a couple of times, but you seem never to have tested this device with it. Odds are in the real world people won't be using gorecord and futzing with audio sync issues. A real review should include evaluation of the product in a "use" environment, not on a test bench for 10 to 20 minutes.

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