Questions about building a new PC to transcode video

[markandjenn]

Sorry in advance for the long post, but I am not really sure where to begin. I did a few searches on this forum and Google for topics relative to this, but I wasn't able to find anything that really helped me.

I am looking into building a new computer to speed up transcoding videos to a TiVo friendly format. My current machine is about 4 years old and is definately slow (Athlon 850MHz, 768 MB RAM, VooDoo 5 graphics card.) Processing a 22 minute Divx or Xvid usually takes about 4 hours on my PC, which I have to assume is extremely slow compared to what other may be transcoding at. I have no interest in playing games on my PC, so I don't need the latest game hardware.

What I would like to know is what are the most important factors in building a PC, so I can prioritize my purchases. The variables in building a PC are:
CPU (Speed, cache, manufacturer, single/dual core, 32/64 bit)
Motherboard (Chipset, front side bus, RAID, SATA)
RAM (Size, speed)
Video Card (Speed, RAM)
Hard Drive (speed, type)

Will a dual core processor transcode twice as fast compared to a single core processor?

Does the video card factor into the transcoding process at all?

What is more important - more RAM or faster processor?

Does the speed of the RAM matter?

Does it matter if the chip is an Intel or an AMD?

Does the front side bus speed matter?

Does the hard drive seek speed make a big difference?

Does the hard drive connection matter (SATA)?

Thank you in advance.

[Cornucopia]

Since you specifically mentioned Transcoding, that narrows it down a bit.

Think of the detailed processes (assuming vid is already captured & edited):

• 1. Fetch frame(s)
  2. Decode to uncompressed space
  3. Gather Bitrate/PSNR/other parameters and save(if 1st of 2pass).
  4. Pre-process (NR, resize, etc)
  5. Encode (if 1pass, or 2nd of 2pass)
  6. Save frame(s)
  7. Repeat

There is some Hard drive and bus activity in the list, but it's minor, and can only be significantly improved by use of RAID striping (esp. if using 2 different sets--1 to read, 1 to write).

The PRIMARY difference is CPU speed.
Dual core or AMD vs. Intel will only help if the software to be used specifically supports those specific extensions. Dual core is no good if the software won't recognize it. If it does, there is a good speed increase (but not a full 2x).
An exception to the "dual core recognition" problem is that you could conceivalby have 2 instances of the same program running--1 for the 1st half of a clip, 1 for the 2nd half--and later merge them together. But this is extra work organizationally.

Next in importance is RAM size. (Speed is of some, but minor significance)
The more RAM you have, the more frames you can cache and minimize the HD seek. The more RAM you have, the more the interim processing can stay in RAM and not be buffered to HD temporarily.

Video card can be important during decoding/playback, but is irrelevant with the great majority of encoding.

Separating media HD's from the OS HD is very important. It's not so important to have it be internal vs. external, as long as the bus/interface speed is already acceptable (most are these days--USB 2.0, Firewire, SATA, SCSI, FibreChannel).

HD size is only important in the need for it all to fit, though you always want to have available "scratch" space.

HTH,

Scott

[bmiller]

You can get a dual core 3.2 ghz.intel,1gb ddr ram,ati vivo,1 sata hard drive for $1200 here in canada from HP.The only thing i would change for what you are after is 2 hard drives.I have an intel 3.0ghz. 2 sata drives an ati vivo,1 gb ddr memory. I have made lots of home video and dual layer dvd backups without a hiccup.Keeping the hard drive defraged is a good thing.An auto defrg tool works well for me.Ever since i started using diskeeper,i've never had any problems.

[harley2ride]

Sorry in advance for the long post, but I am not really sure where to begin. I did a few searches on this forum and Google for topics relative to this, but I wasn't able to find anything that really helped me.

I am looking into building a new computer to speed up transcoding videos to a TiVo friendly format. My current machine is about 4 years old and is definately slow (Athlon 850MHz, 768 MB RAM, VooDoo 5 graphics card.) Processing a 22 minute Divx or Xvid usually takes about 4 hours on my PC, which I have to assume is extremely slow compared to what other may be transcoding at. I have no interest in playing games on my PC, so I don't need the latest game hardware.

What I would like to know is what are the most important factors in building a PC, so I can prioritize my purchases. The variables in building a PC are:
CPU (Speed, cache, manufacturer, single/dual core, 32/64 bit)
Motherboard (Chipset, front side bus, RAID, SATA)
RAM (Size, speed)
Video Card (Speed, RAM)
Hard Drive (speed, type)

Will a dual core processor transcode twice as fast compared to a single core processor?

Not at the present time, but possibly in the future. If the price difference is minimal, go for the dual core.

Does the video card factor into the transcoding process at all?
If you use one of the ATI AIW cards it does. It can do both functions well.


What is more important - more RAM or faster processor?
Processor speed is important, but I wouldn't go with anything less than 768mb of ram.

Does the speed of the RAM matter?
To a degree. Faster ram is always better as encoding is very memory intensive.

Does it matter if the chip is an Intel or an AMD?
Not really! Matter of preference.

Does the front side bus speed matter?
Yes but not a huge issue.

Does the hard drive seek speed make a big difference?
As long as you are using at least ata100, you will be ok.

Does the hard drive connection matter (SATA)?
Some people have problems with sata due to chipset/driver issues. I use sata and it works just fine. Benefit is minimal.

Thank you in advance.

[markandjenn]

Wow! That is a lot of help. Thank you for all of the responses.

Follow up questions:

It doesn't matter where the application that is doing the transcoding is, correct? The program would be loaded into RAM and it should not matter right?

If I do get a dual core processor, would I be able to continue using the PC, like surfing the web or working in Office with little to no delay? Right now, if I am transcoding I can't do anything else without doubling the time it takes to transcode.

Can I assume that a large cache on the CPU would also provide a benefit as well as the CPU is the main bottleneck of the transcoding process?

How long does it take to transcode a 30 minute Divx file to MPEG2 on your PC? I mentioned mine takes 4+ hours. If it will still take that long, maybe I don't need to bother. I have to assume that it is much faster on your PC.

[INFRATOM]

When building a computer for DV editing, you can never get enough. My suggestion is to stretch your $ budget and hardware. Meaning if you concluded you need certain CPU or else go one step higher before you know it you close the gap. The cost to upgrade is a lot more and doesn't worth it because you have to get rid of the part you have and you have paid double. Having said all that you need:
Fastest CPU and hard drive setup you can afford + 1 GB dual RAM.
Computer has gone to a new technology so you have to decide on the componants. Video processing is mostly CPU harddrive process.
Question on speed, if you find a program that is optimized for double cpu you get very noticable speed difference. Pentium generally is better for video but price wise AMD64 could be better choice on the lower scale.
The first step is to make choice on technology and shop for parts see how much you come up with. Buy a good motherboard and good one comes with everything like firewire USB2 and all also gives you easy overclocking option. One good reference is Toms hardware guide and Anandtech they give you examples test on componants. My final suggestion Don't compromise and buy more than what you need today and avoid fading technology.

[harley2ride]

Watch for deals too. A few weeks ago I got a buddy of mine a dell 9100 dual core 3ghz, 1ghz ddr, gt6800, 20"lcd 5.1 speakers, 160gb sata, dvd-rom and dvd burner, firewire, usb 2.0, for $1100.00 delivered.

[edDV]

...
The PRIMARY difference is CPU speed.
Dual core or AMD vs. Intel will only help if the software to be used specifically supports those specific extensions. Dual core is no good if the software won't recognize it. If it does, there is a good speed increase (but not a full 2x).
An exception to the "dual core recognition" problem is that you could conceivalby have 2 instances of the same program running--1 for the 1st half of a clip, 1 for the 2nd half--and later merge them together. But this is extra work organizationally.

Next in importance is RAM size. (Speed is of some, but minor significance)
The more RAM you have, the more frames you can cache and minimize the HD seek. The more RAM you have, the more the interim processing can stay in RAM and not be buffered to HD temporarily.

I would fully agree on CPU, but only high end software is multi-core aware and sometimes difficult to use. I would expect encoders (transcoders) to take advantage of the new generation multi-core chips soon. Many have expensive versions that run on dual G5 or dual Xeon now.

I somewhat disagree on RAM after reaching 512MB-1GB. I haven't seen a benchmark that rewards more RAM with current encoder implementations.

...
Having said all that you need:
Fastest CPU and hard drive setup you can afford + 1 GB dual RAM.
Computer has gone to a new technology so you have to decide on the componants. Video processing is mostly CPU harddrive process.

I would agree on CPU but hard drive speed has little to do with transcoding other than the short time it takes to load the file. Processing runs at a snails pace relative to today's mid-speed drive.

For an encoding machine I would focus on CPU, not on hard drive beyond separating OS and video access to separate drives. Video capture needs a HDD system fast enough for realtime capture. Today, RAID is only a requirement for multi-stream SDI processing.

[redwudz]

All good suggestions. If I were building a new machine now, I would be tempted by the dual core 64 bit AMD CPUs, though not much (If any) software takes advantage of them presently. The socket A and socket 754 AMD CPUs are towards the end of their life cycle and I would avoid them. (Sorry, I'm prejudiced toward AMD, I like their value for performance)

I also like Asus motherboards, but there are a lot of good choices out there. 512Mb is enough memory, but going to 1000Mb doesn't cost much more.

I like a minimum of 2 hard drives, SATA is inexpensive and most motherboards that have it have PATA controllers also, so you have more options.

A good name brand power supply. ~450W is good. A roomy case with good ventilation is nice.

If you look into AMD 64 CPUs, most motherboards that use them also use PCI-E video cards, just something else to consider.

This would be mostly if you were going to build a PC. It's not that hard. If not, look around, there are lots of good deals on manufactured PCs. Just make sure you are getting what you want.

[markandjenn]

Thanks to all here who helped me make a decision on my new computer.

I ended up going with an AMD 3700+ San Diego Processor ($210) with an Asus A8N-VM CSM ($82) motherboard and 1 GB Kingston RAM ($72).

I went with the fastest processor I could buy. The dual core AMD chips are just too expensive right now. The Intel dual cores run too hot at to low speeds for me to worry about them. The Asus motherboard has the ne nVidia 6150 video processor that handles HD video with a DVI-D out, Firewire port and Gigabit LAN.

For now, I will keep my IDE hard drives, DVD burners, case and 400 watt power supply. I will upgrade to SATA and add a video card when I can.

Thanks again for all the help.

[jagabo]

The slowest Athlon 64 X2 (dual core) processor is currently as fast or faster than the fastest Intel (dual or not) processor, even with video transcoding (which used to be Intel's domain).

XVID:
http://www.tomshardware.com/2005/11/21/the_mother_of_all_cpu_charts_2005/page32.html

WMV:
http://www.tomshardware.com/2005/11/21/the_mother_of_all_cpu_charts_2005/page33.html

Mainconcept:
http://www.tomshardware.com/2005/11/21/the_mother_of_all_cpu_charts_2005/page34.html

Of course, different encoders may give you different performance. Check out the software you'll be using.

I often use TMPGEnc Plus and I find that it encodes nearly twice as fast when using both cores of my A64 X2 3800+ (you can run the program single or multithreaded).

If you're really doing a LOT of transcoding it doesn't matter if your software is multithreaded if you can run multiple instances of your software at the same time. For example, you can run two instances of VirtualDub to nearly double the throughput.

[markandjenn]

Just to post an follow up of performance. Encoding 5 22 minute television shows through NeroVision to DVD used to take 11-12 hours on my old PC (AMD 850 MHz with 512 MB RAM). The old machine would not be able to do anything but encode. The new machine takes about 2.5 hours and I can still use the PC for other uses while it is encoding. This is so much nicer.

[jagabo]

Just to post an follow up of performance. Encoding 5 22 minute television shows through NeroVision to DVD used to take 11-12 hours on my old PC (AMD 850 MHz with 512 MB RAM). The old machine would not be able to do anything but encode.

Why is that? Couldn't you use Task Manager to reduce the process priority?