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Hardware-based encoders probably won't give you a noticeable difference in quality (though they might) but they will allow you to get away with a much slower CPU. TiVo, ReplayTV and other pre-built DVR's use hardware encoders along with ridiculously slow CPU's that do nothing but basically power the menu interface and process remote control inputs.

It's just a tradeoff. With a hardware encoder you put the processing power on the card vs. on your CPU. Without a hardware encoder, you need a very fast CPU to capture at the highest resolutions with de-interlacing on, while also watching a previously recorded show at the same time. Software encoders just capture the raw signal and pass it on to the CPU for encoding.

I don't know that one is really better than the other; I think it depends on the rest of the PC you either already have or are planning to build. If you've got a 3mhz CPU already, you may as well not waste the money on a hardware encoder card, as that's plenty of power for doing pretty much anything you'd want with Myth, even with more than one tuner. But if you're building from scratch, you may be able to save some money overall and still get excellent quality by going with something like the PVR-250.


-----Original Message-----
From: Tony Mahar [mailto:amahar@snet.net]
Sent: Thursday, July 24, 2003 11:01 AM
To: mythtv-users@snowman.net
Subject: [mythtv-users] Capture Card Advice


Hello all,

I am new to PVR on PC, but am very excited. I am switching from my satellite TV based PVR (dish 501 pvr) to regular analog cable.

What setup provides the best capture quality at 29.7x fps NTSC?

Would it be boards like Hauppauge PVR 350 with mpeg encoders? Or are the encoders on the hardware chips poor, and then would a software encoder with a fast machine be capable of cleaner encoding?

Thanks,
Tony


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One thing that is plus with software encoder is the use of MPEG4 which
creates alot smaller files for the same quality. My XP1700 works great
with live tv.

Cheers,
Joel

Jeff Williams wrote:

>Hardware-based encoders probably won't give you a noticeable difference in quality (though they might) but they will allow you to get away with a much slower CPU. TiVo, ReplayTV and other pre-built DVR's use hardware encoders along with ridiculously slow CPU's that do nothing but basically power the menu interface and process remote control inputs.
>
>It's just a tradeoff. With a hardware encoder you put the processing power on the card vs. on your CPU. Without a hardware encoder, you need a very fast CPU to capture at the highest resolutions with de-interlacing on, while also watching a previously recorded show at the same time. Software encoders just capture the raw signal and pass it on to the CPU for encoding.
>
>I don't know that one is really better than the other; I think it depends on the rest of the PC you either already have or are planning to build. If you've got a 3mhz CPU already, you may as well not waste the money on a hardware encoder card, as that's plenty of power for doing pretty much anything you'd want with Myth, even with more than one tuner. But if you're building from scratch, you may be able to save some money overall and still get excellent quality by going with something like the PVR-250.
>
>
>-----Original Message-----
>From: Tony Mahar [mailto:amahar@snet.net]
>Sent: Thursday, July 24, 2003 11:01 AM
>To: mythtv-users@snowman.net
>Subject: [mythtv-users] Capture Card Advice
>
>
>Hello all,
>
>I am new to PVR on PC, but am very excited. I am switching from my satellite TV based PVR (dish 501 pvr) to regular analog cable.
>
>What setup provides the best capture quality at 29.7x fps NTSC?
>
>Would it be boards like Hauppauge PVR 350 with mpeg encoders? Or are the encoders on the hardware chips poor, and then would a software encoder with a fast machine be capable of cleaner encoding?
>
>Thanks,
>Tony
>
>
>_______________________________________________
>mythtv-users mailing list
>mythtv-users@snowman.net
>http://lists.snowman.net/cgi-bin/mailman/listinfo/mythtv-users
>
>

Thanks Jeff,

I guess my question comes down to is this: obviously, a software encoder can
potentially produce a better image given enough computing power, with little
to no artifact, smearing, or ghosting problems on the encode side, and good
de-interlacing of the source image. Since the hardware encoders are fixed
silicon (unless there's a pga in there), are they at a fixed compression
mode or do they allow different compression levels of the mpeg encoding.

Thanks,
Tony
-----Original Message-----
From: mythtv-users-bounces@snowman.net
[mailto:mythtv-users-bounces@snowman.net] On Behalf Of Jeff Williams
Sent: Thursday, July 24, 2003 11:18 AM
To: Discussion about mythtv
Subject: RE: [mythtv-users] Capture Card Advice

Hardware-based encoders probably won't give you a noticeable difference in
quality (though they might) but they will allow you to get away with a much
slower CPU. TiVo, ReplayTV and other pre-built DVR's use hardware encoders
along with ridiculously slow CPU's that do nothing but basically power the
menu interface and process remote control inputs.

It's just a tradeoff. With a hardware encoder you put the processing power
on the card vs. on your CPU. Without a hardware encoder, you need a very
fast CPU to capture at the highest resolutions with de-interlacing on, while
also watching a previously recorded show at the same time. Software
encoders just capture the raw signal and pass it on to the CPU for encoding.

I don't know that one is really better than the other; I think it depends on
the rest of the PC you either already have or are planning to build. If
you've got a 3mhz CPU already, you may as well not waste the money on a
hardware encoder card, as that's plenty of power for doing pretty much
anything you'd want with Myth, even with more than one tuner. But if you're
building from scratch, you may be able to save some money overall and still
get excellent quality by going with something like the PVR-250.


-----Original Message-----
From: Tony Mahar [mailto:amahar@snet.net]
Sent: Thursday, July 24, 2003 11:01 AM
To: mythtv-users@snowman.net
Subject: [mythtv-users] Capture Card Advice


Hello all,

I am new to PVR on PC, but am very excited. I am switching from my
satellite TV based PVR (dish 501 pvr) to regular analog cable.

What setup provides the best capture quality at 29.7x fps NTSC?

Would it be boards like Hauppauge PVR 350 with mpeg encoders? Or are the
encoders on the hardware chips poor, and then would a software encoder with
a fast machine be capable of cleaner encoding?

Thanks,
Tony


_______________________________________________
mythtv-users mailing list
mythtv-users@snowman.net
http://lists.snowman.net/cgi-bin/mailman/listinfo/mythtv-users

> I guess my question comes down to is this: obviously, a software
> encoder can
> potentially produce a better image given enough computing power,
> with little
> to no artifact, smearing, or ghosting problems on the encode
> side, and good
> de-interlacing of the source image. Since the hardware encoders are fixed
> silicon (unless there's a pga in there), are they at a fixed compression
> mode or do they allow different compression levels of the mpeg encoding.

The PVR-250's use a fully programmable compression engine that uses firmware
that you download to the card when you load the drivers. You can select all
aspects of the resulting MPEG2 stream, the size of the captured images, as
well as the bitrate of the stream. Selecting a lower bitrate reduces quality
and also results in much smaller captures. Capturing at DVD quality @ 720 x
480 takes about 4GB per hour on my PVR-250.

The other thing to consider is how to support multiple tuners. Using
PVR-250's I can use 4 of them simultaeously on two very slow backend
machine. Doing this with POT's (Plain Old Tuners) would require a lot of CPU
power.

Dennis

> Thanks Jeff,
>
> I guess my question comes down to is this: obviously, a
> software encoder can
> potentially produce a better image given enough computing
> power, with little
> to no artifact, smearing, or ghosting problems on the encode
> side, and good
> de-interlacing of the source image. Since the hardware
> encoders are fixed
> silicon (unless there's a pga in there), are they at a fixed
> compression
> mode or do they allow different compression levels of the
> mpeg encoding.

Well, just to clarify the answer someone else gave - hardware decoders will allow you different levels of compression but you are locked in to whatever codec is programmed into the chip. I am not sure if this is upgradeable via firmware or whatever but in any case you will at least be at the mercy of the card manufacturer. So the answer to your question seems to be yes, they are at a fixed compression mode - though the compression quality can be adjusted.

I would personally rather be able to use MPEG4 decoding, so if I was to do it over again I'd probably still buy a fast CPU and a software decoder card that only captures raw signal and lets the software determine the codec used.


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Jeff Williams wrote:
>>Thanks Jeff,
>>
>>I guess my question comes down to is this: obviously, a
>>software encoder can
>>potentially produce a better image given enough computing
>>power, with little
>>to no artifact, smearing, or ghosting problems on the encode
>>side, and good
>>de-interlacing of the source image. Since the hardware
>>encoders are fixed
>>silicon (unless there's a pga in there), are they at a fixed
>>compression
>>mode or do they allow different compression levels of the
>>mpeg encoding.
>
>
> Well, just to clarify the answer someone else gave - hardware decoders will allow you different levels of compression but you are locked in to whatever codec is programmed into the chip. I am not sure if this is upgradeable via firmware or whatever but in any case you will at least be at the mercy of the card manufacturer. So the answer to your question seems to be yes, they are at a fixed compression mode - though the compression quality can be adjusted.
>
> I would personally rather be able to use MPEG4 decoding, so if I was to do it over again I'd probably still buy a fast CPU and a software decoder card that only captures raw signal and lets the software determine the codec used.

To clarify the clarification. An MPEG-2 Hardware solution only does
MPEG-2. MPEG-2 was developed originally for the broadcast market. The
development was incubated from work originally done here at the David
Sarnoff Research Center, formally RCA Laboratories, now Sarnoff
Corporation, and others. Direct TV was the first commercial product
that used a preliminary (and slightly incompatible) MPEG-2 stream, but
once MPEG-2 was ratified, they changed their systems over to it. Almost
all current hardware MPEG-2 encoders are all roughly equivalent. The
main differences are how it does motion estimation (which can take > 60%
of the overall cycles), the rate control system, and some of the more
advanced tools (such as dual-prime vectors, scenecut detection, inverse
3:2 pulldown, etc.) Bottom line is that for CCIR601 (720x480) once the
bit-rate exceeds 8Mbs or so, there is plenty of overhead to correct
errors caused by mediocre encoders. It's only when the bitrate gets
below 4Mbs that better encoders start showing their true colors (pun
intended).

MPEG-4 started out as a replacement for H.263 (video conferencing), but
it grew to encompass MPEG-2's domain as new compression techniques were
introduced. The current state of MPEG-4 seems to be a mishmash of
profiles and levels. I haven't seen any MPEG-4 decoder or encoder (sans
reference software) that covers any complete profile/level. The real
advantage of MPEG-4 comes with smaller resolutions because of smaller
block sizes, and lower bitrates (due to tools like global motion). It
has some really nifty capabilities, like the ability to send multiple
resolutions at the same time and sprites. In all it's glory, a
streaming MPEG-4 encoder can negotiate with the decoder to select the
tool set and encoding parameters on the fly. Any hardware solution that
implements the full spec will be one hot sucker. MPEG-4 starts showing
off as the bitrate goes down, mainly due to the ability to drop frames.
This isn't bad for video conferencing, but I surely don't want to
watch a movie at 6 fps or less. Even standard 24 fps of film looks a
bit choppy at the higher illumination of a normal home viewing condition
(that's one reason why they darken a movie theatre).

However, if you really want to look at a spec that is a culmination of
everyone's pipe dream, take a look at the new JVT spec. Yeehaw!

Gary