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MPEG2 Software/Hardware

 
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oficinadamidia



Joined: 27 Mar 2003
Posts: 2
Location: Brazil

PostPosted: Thu 27 Mar 2003, 16:27    Post subject: MPEG2 Software/Hardware Reply with quote

I will intend to buy a Matrox RTX-100.
I am very happy with TMPGENC/Rui del-Negro Guide, I would like to know if matrox rtx100 with CCube encoder, can have the same quality of compression as TMPGENC/Rui del-Negro Guide. Question
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Tue 1 Apr 2003, 16:34    Post subject: Reply with quote

It's very hard for a hardware compressor (especially a real-time compressor) to have the same quality as a software compressor. For three reasons:

1. Hardware compressors usually do not let you adjust all the settings, so you cannot adapt the configuration to your footage.

2. Real-time hardware compressors are optimised for speed. They have to be able to encode each frame in 1/25th (or 1/30th) of a second. This means their algorithms usually take some "shortcuts". I suspect most real-time encoders use a search algorithm similar to TMPGEnc's "motion estimation". It's not bad, but it's not as good as the "highest quality" motion search.

3. Real-time hardware compressors must work in single-pass mode. Using a software encoder in 2-pass mode ensures that the bitrate is well distributed along the video. In single-pass mode the compressor can use too many bits for the beginning of the video, and not have enough left for the end of the video (so the quality gets worse).

In practical terms, a hardware encoder will usually give you good results if you use high bitrates and short clips (ex., if your videos are under 1 hour, they will probably look good with a hardware encoder). If your videos are bigger (ex., 90 or 120 minutes), then a good software encoder (such as TMPGEnc or CCE SP) operating in 2-pass mode will give you much better results than a hardware compressor (*).

I think the RT.X100 can capture in DV, so for longer projects you can always capture in DV and then encode using TMPGEnc, and for shorter projects, use the hardware MPEG-2 compressor. From what I've read about the RT.X100, it's a pretty good card, but I've never used one personally.

(*) Note: there are some high-end hardware encoders that are actually a mix of hardware and software, and can do 2-pass hardware-assisted encoding. These are very rare and very expensive, though, so what I said above applies to most "consumer" hardware encoders.

RMN
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MJB



Joined: 21 Feb 2003
Posts: 33
Location: Pensacola Florida

PostPosted: Sat 5 Apr 2003, 1:02    Post subject: Mpeg Encoders Decoders Reply with quote

Hello, We use the encoder / decoder cards made by Adtec in Jacksonville Florida. The cards are actually made in Isreal. We copy anaolg out from the editor through these cards. For 30 minutes it takes 90 minutes to encode. It is top quality Mpeg. This operation works for a full power broadcast tv station. Now for the punch, these cards costs $11,000.00 each.

As RMN said, software encoding is where it's at.
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shadysamir



Joined: 28 May 2003
Posts: 8
Location: Cairo - Egypt

PostPosted: Wed 28 May 2003, 12:30    Post subject: Sonic SD2000 Reply with quote

The Sonic SD2000 card is (as Sonic claims) what the industry uses for commercial releases. All the features of the card are great (in a brochure) and the price is $25,000. It is a hardware-assisted software encoder. I wonder if this stuff is worth the cash.
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RMN
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Joined: 04 Feb 2003
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PostPosted: Fri 30 May 2003, 21:52    Post subject: Reply with quote

Unless you need to turn out several movies a day, faster than real-time, I would say it's not.

A fast system (ex., dual Xeon or dual Athlon) will encode nearly in real-time using only the main CPUs (i.e., using a "software-only" encoder). CPUs keep getting faster so, in a year or so, I'd say you 'll be able get top-quality real-time encoding with a single-CPU system (ex., an Athlon 64). In other words, unless the extra speed "pays for itself" within a year, it's probably not a very good investment.

Hardware-assisted encoding may have some life left in it if HDTV becomes more common, since it needs about 3x more computing power to encode.

RMN
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Josse



Joined: 29 Apr 2003
Posts: 9

PostPosted: Fri 30 May 2003, 22:21    Post subject: Reply with quote

rmn wrote:
Unless you need to turn out several movies a day, faster than real-time, I would say it's not.

A hardware encoder, being a capturing device, will be as-fast-as real time at best Wink (slower when it is doing segment re-encoding). But as they are capturing and encoding at the same time, they will always be faster than the fastest software encoder (for which you have to capture first).

An advantage of a hardware encoder is that it can capture directly from higher quality video than the DV most of us are using, without first creating humongous files on the harddrive. Expensive hardware encoders also will have very good algorithms and a number of dedicated processors to execute these. But forgetting about return on investment for a moment, with DV or similar as source there is little point in using a hardware encoder apart from time saved.
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RMN
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PostPosted: Fri 30 May 2003, 23:24    Post subject: Reply with quote

Josse wrote:
A hardware encoder, being a capturing device, will be as-fast-as real time at best Wink


Ah... but a professional hardware-assisted encoder is usually not a capture device. Smile

In the land of the high-end, video is normally captured to an uncompressed format (sometimes it's not even video, it's digitised film) and the hardware-assisted encoder is used only to convert it to MPEG-2.

And good encoders do indeed encode faster than real-time. The general idea is you capture once, encode, look at the result, tweak settings for specific scenes / segments, encode again, tweak again, etc., until you're happy with the result. For this process to be efficient, you need the encoding process to be as fast as possible. Even some software-only encoders (CCE SP, for example) manage to encode faster than real-time in high-end hardware. To be worth the price, hardware-assisted encoders need to be faster than that.

Josse wrote:
An advantage of a hardware encoder is that it can capture directly from higher quality video than the DV most of us are using,


Er...? And are you saying that I can't use a software encoder (such as TMPGEnc) to encode something captured from Beta Digital, or from uncompressed D1, or from HD, or from film?

Josse wrote:
without first creating humongous files on the harddrive.


Hard drive space is terribly cheap these days. 1 minute of uncompressed D1 needs about 1 GB. That means that a single 250 GB drive can hold 4 hours of uncompressed video. With a RAID you can easily have more than 1 TB of storage.

Josse wrote:
Expensive hardware encoders also will have very good algorithms and a number of dedicated processors to execute these.


What distinguishes a generic hardware MPEG-2 encoder (ie, a MPEG-2 capture card) from a high-end hardware-assisted encoder is programmability. While MPEG-2 capture cards typically have hardwired algorithms, high-end encoders have all their algorithms defined by the software component (a program or driver), and the hardware consists of a group of processors especially suited to typical encoding operations. This means that a new version of the software can significantly improve the output, while still using the hardware you have to speed up the individual calculations.

In fact, I suspect it would be possible to use parts of modern graphics processors (the programmable shaders) to speed up part of the MPEG encoding process.

RMN
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Josse



Joined: 29 Apr 2003
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PostPosted: Fri 30 May 2003, 23:37    Post subject: Reply with quote

I thought we were talking about the Sonic SD-2000 which captures to MPEG via SDI.
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shadysamir



Joined: 28 May 2003
Posts: 8
Location: Cairo - Egypt

PostPosted: Fri 30 May 2003, 23:42    Post subject: Reply with quote

I will have to agree with rmn. We own 2 (discontinued) Pinnacle DC2000 boxes and the process of capturing in MPEG2 was really appealing UNTIL you examin the results carefuly. Let alone the fact that it does not have digital inputs. Still it's a nice MPEG2-IBP editing box (if not the only).

We ended up getting an uncompressed editing machine for capturing and editing then throwing the results to Procoder. I am willing to give TMPGEnc a try now.

We still use the DC2000 boxes for mass encoding. The results are not THAT bad.
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RMN
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Joined: 04 Feb 2003
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PostPosted: Sat 31 May 2003, 2:05    Post subject: Reply with quote

Josse wrote:
I thought we were talking about the Sonic SD-2000 which captures to MPEG via SDI.


Never used an SD-2000; was talking about hybrid software-hardware encoders in general.

Most high-end authoring systems have separate capture and encoding boards, so that you can try different encoding settings without having to re-capture. You can usually do both operations simultaneously, but I don't see anyone doing that for any important project. The whole point of having a fast hardware-assisted encoder is to be able to fine-tune the settings and try different encodings without having to wait too long. Not to mention doing 2-pass encoding.

If you're going to use "automatic" real-time MPEG-2 capture, you might as well go with a (relatively) cheap Pinnacle card.

RMN
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shadysamir



Joined: 28 May 2003
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Location: Cairo - Egypt

PostPosted: Sat 31 May 2003, 11:21    Post subject: Reply with quote

Josse wrote:
I thought we were talking about the Sonic SD-2000 which captures to MPEG via SDI.


I was talking about the Pinnacle DC2000 as an example of capture card + realtime encoding (+ IBP editing). Even the Sonic SD2000 does not capture into MPEG2 directly if you want to get the high quality stream you actually paid all the money for.
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