[Question] Why quality difference converting DV and mpg2 ?

[Pyromarkus]

Hi there,

I read a lot in this forum, found some answers but nothing satisfied me for my problem:

When converting DV (which I captured from my Sony camcorder via firewire to harddisk as AVI) with bbmpeg or TMPEnc to MPEG2 suitable for standard SVCD I get very good video quality with still pictures without much movement. When there is movement, the picture gets really bad, blocky and pixelized.

Ok, there are much hints in this forum, like "try with higher bitrate, try XSVCD, try hardware capture card"...

But - when ripping any DVD (with DVDx for example) which has some bbmpeg routines for encoding, the quality of that videos are georgeous at any time, even with much movements there is only minimal pixelization.

So my questions:

What is the difference when encoding DV (captured and saved with DV Video Encoder with 3750 kb/sec) and encoding DVD-MPEG2???

Both are encoded with 2350 to 2600 kb/sec and the quality is so different! Is it, because the DVD is already encoded with an high quality mpeg2-encoder of the film industry and TMPEnc only has to reduce the bitrate a little?
Is it, because AVI is compressed? But 3750kb/secs is still much more than the 2350 of the SVCD-mpeg2 bitstream?


Is there any fair chance, to get similar results compared to ripped DVDs when encoding my camcorder captures to MPEG2 for SVCDs?

Thank you in advance,
hope to get some quality answers

Markus

P.s.: Strange world - ripping DVDs works fine - I don't want to do that - but my own videos are so bad...

[fonoop]

Well, you're not the only one with that problem. I thought it was beacuse my dvd player(Panasonic RV31U-K) didn't support svcd that well. Anyway, its the same problem with me, the svcd sample works fine, but my dv movies encoded with TMPEnc are blocky when there is movement. Possibly a problem with TMPEnc, I dunno. I'll try encoding with Ulead VideoStudio 6 and see if a different encoder helps. Sorry I can't help you, might have an answer in a few hours.

[ImaWeTodd]

Hey Pyro,

I have the same problems

For me it boils down to: My source sucks compared to DVD!

I have a TRV900 (good camera) but here are some of the
stumbling blocks I've had:
- Captured video is interlaced which is much harder to convert
(especially if you resize) without loosing too much info.
- My camera capture resolution is much worse than studio cameras under
perfect light. (I chased jaggy lines in svcds for a while until i found
it was mostly in my source)
- The camera man (me) shakes way too much and does too many
pans. Movement = changeing scene = lotts a bits.

What do i do about this?
1) Watch the source on the TV to know what I am starting with.
2) Try to go with the captured resolution (no resize) and stay interlaced.
Ya need an xsvcd dvd player for this.
3) Crank up the bit rate. 3000 seems to be a min for me. Disk size isn't
a problem because > 20min of my stuff can clear a room.

[Greg12]

dv is a loseless "data transfer" that is used by camercorders via Firewire.

MPEG 2 is a lossy encoding used by DVD's and Digital TV

DV will not play on any set tops

[ImaWeTodd]

Guess what...

If you have a DV camcorder that has s-video out,
you can plug the darn thing right into ya TV! I don't know how they do it


Man these things are soooo slick. I hear tell on the new ones you
can do "real-time transcoding" or analog->digital "pass-through",
(Basically run your analog source thru ya camcorder out the firewire
to the pc !) Wow who needs a capture card? We acutally my TRV900
doesn't do this cause it's old

So for me: DV is 720x480 pixels, 30 fps (NTSC) which is what gets captured by my camcorder and saved onto a 60min tape. BTW, that
works out to a fixed data rate of 3.6 MBytes/sec or 13gig for one of them
little tapes!

216MB/min wow! Even that is compressed at 5:1 so ya better have a bunch
of HD space for those AVIs. if you can't preview them on your TV.

[Pyromarkus]

What do i do about this?
1) Watch the source on the TV to know what I am starting with.
2) Try to go with the captured resolution (no resize) and stay interlaced.
Ya need an xsvcd dvd player for this.
3) Crank up the bit rate. 3000 seems to be a min for me. Disk size isn't
a problem because > 20min of my stuff can clear a room.

So the difference between encoding DV and DVD is mainly:
DV is interlaced, DVD is progressive?

That's why ripped DVDs are much better encoded then own camcorder captures?!
So without breaking the SVCD standard I won't be able to get better quality?

BTW - I have the TRV900 too - and a tripod.
The whole things sounds very unsatisfiying...

Markus

[ImaWeTodd]

Pyro,

Hey great camera huh?!

Have you viewed your DV directly on your TV?
I can get close to that with SVCD if I don't muck with it much.

I can get farily good stuff if I:
- Have good light and a stable camera
- Keep it interlaced and 720x480 resolution
- Adjust the color saturation and contrast a bit because
most TVs are out of wack when it comes to colors/brightness/etc.

The problem for me is the 1st step. When I'm filming the
kiddies, I'm just not workn the camera well.

Have you checked out ttp://www.bealecorner.com/trv900/index.html ?

Great link for info on the TRV900.

Have you ever encoded interlaced source to SVCD? Get a hold of
some TV show DVDs and give them a try (Barney is my speed). I'm
not talkn IVTC. Work on a resize and keep them interlaced. I find this
verrry difficult. I think if you could do this well and with good lighting
you may be able to do a standard SVCD.

For me this was too much work and I havn't got it right .
Instead I just bought an apex type player and make xsvcd.
I may at some time buy a dvd-r burner. That should give better
compatability.

[Xesdeeni]

Back to Pyromarkus' original question...How can we get DV to look as good as DVD?

I have wrestled with the same question and come up with the following (all this applies to NTSC only):

1. DVDs are almost all from film. Film is 24 Fps (frames per second). The MPEG2 stream is encoded on the DVD as 24 Fps. The player does the 3:2 pulldown to convert the 24 Fps to 60 fps (fields per second).

However, DV is normally already 60 fps. The MPEG2 stream is therefore encoded on the DVD as 60 fps.

First, this is 25% more data, so the bits must be spread thinner.

Second, because the MPEG2 stream is encoding 60 fields every second there appears to be more overhead. It is unclear to me whether this is MPEG overhead for each field/frame, or if this is because the relationship of successive fields is spatially offset (up and down by a line), causing the MPEG encoder to have to encode what seems to be motion but really isn't. Either way, there is definitely a quality difference between taking the same (30 Fps) video and encoding it as 30 Fps and as 60 fps.

2. The DV video is much more noisy than a typical film print.

First, the sensors (CCDs) on a typical camcorder have a higher noise floor than professional cameras or film. Worse still, your home movies are normally shot in ambient light, which means the gain on the sensor must be raised, further increasing the noise floor. My tests have shown that outdoor shooting in sunlight has less noise than indoor shooting with indoor lighting. I also assume that a more expensive (i.e. 3-sensor) camera would produce less noise, but I don't really have any way of verifying this myself.

Second, DV is compressed in a manner similar to JPEG. This is a lossy technique that introduces even more noise into the image. If you want to see this, use a DV codec (like the MainConcept one) and encode some artificial video (like a rendered scene). Then compare the before and after and you'll see the noise.

3. Many DVDs are actually letterboxed, even though they are anamorphic. Apparently very few films are/were shot in 16:9. Most use wider aspect ratios than that. As a result, to fit the entire image on the screen, even on a 16:9 TV, the film must be letterboxed. Obviously this further reduces the amount of data that needs to be encoded.

4. Most DVDs are encoded with hardware. In another thread ( http://forum.vcdhelp.com/viewtopic.php?t=79162 ) the assertion was made that the hardware encoders were probably only faster, not necessarily better, than software encoders. While that may be true of consumer-level hardware encoders, that's not true of professional encoders.

MPEG involves many choices on the part of the encoder. The decoder just decodes what is there, but the encoder must determine how, from a number of choices, to encode a particular frame. This is why we can play MPEG in real time with software, but we normally can't encode it in real time with software on the same machine. It is an asymetrical compression technique (unlike JPEG and DV, which is symetrical).

Anyway, software encoders must cut corners to make these decisions. They make broad assumptions for the sake of speed. However, a hardware encoder can actually take all the decision paths at the same time. They can encode the video in all of the methods possible (or at least several of the best) in parallel and make the decision on which one is best based on the results. This is because the hardware can have parallel paths within it that encode in multiple ways and make decisions all at the same time. In order for software to do this, it would have to try each encoding path sequentially and then make the decision afterwards. This would make things even slower than they already are (although the quality would go up), so they don't do this.

Of course, the machine could have multiple processors and the software could be written to take advantage of them, but then that would severely limit the market.

Anyway, here are some suggestions for trying to get DV-based DVDs closer to commercial DVD quality:

1. If your camera has a progressive shooting mode, use it when appropriate. This will allow you to encode the MPEG stream as 30 Fps instead of 60 fps.

Of course, if you are shooting your kid playing sports, you probably don't want to do this, because that action won't be as smooth. But you'll have to experiment to see whether you like the way it looks.

If your camera doesn't have a progressive mode, you could try deinterlacing the image before encoding. However, this is a mixed bag:

Since you normally are dealing with hand-held devices, the image will probably not be steady. That means that a smart deinterlacer will not really be able to find any coorelation between successive fields most of the time. It will just have to either interpolate one field or blend both fields. So you might be just as well off with a dumb deinterlacer (which should process faster than a smart one). Either way, the vertical resolution will be degraded. It's a tradeoff.

2. Shoot in as much light as possible. Whenever I shoot, I turn on all the lights in the room, and if it is daytime in a room with windows, I open the blinds to flood the room with light. This helps lower the gain on the CCD so that the noise floor is lowered.

Beyond that, we could all step up to the 3-CCD cameras, but my checkbook won't let me right now

3. Use a noise filter. TMPGEnc's filter is too slow, and I haven't really seen CCE's filter do much good, so I normally frameserve from VirtualDub. My experiments have shown that the spatial filters are the most useful for DV video. I normally stay away from the built-in filter, because it can't seem to handle text (titled, etc.) without screwing up the edges in an inconsistent (noticeable) way. But it is one of the fastest. And again, because the video is normally not very steady, temporal filtering just gets confused and actually adds more noise than it eliminates.

4. Use a higher bitrate. I think we will all have to face it that we won't get much more than an hour of DV-sourced video onto our homemade DVDs if we want commercial DVD quality. That represents about an 8-9Mbps (megabit per second) data rate, which is near the DVD maximum. Two hours is about 4-4.5Mbps, and my experiements have shown this is definitely lower quality than commerical DVDs even with all the work I've done. Of course the quality is much better than anything else (like VHS), so it's all relative.

5. Get a hardware encoder. This is what I have in mind myself, but it's extremely tricky. As has been pointed out in the thread above, there aren't really many cards that encode MPEG from a digital stream on your hard drive (normally an edited DV stream). But worse than that, how do you make sure the quality is actually better than one of the software encoders after you've plopped down several hundred dollars for some hardware? Since my local stores don't carry too many of these, the buy and return path is complicated by the prospect of mail-ordering the devices. I don't have the answer to this one yet, but I'll let you know if/when I do.

Xesdeeni

[vhelp]

hay pyro,

>> So the difference between encoding DV and DVD is mainly:
>> DV is interlaced, DVD is progressive?
* Not necessarily.
* DV can be INTerlaced or PROGressive
* Min DV cam is INTerlaced. I know how to encode pretty good
quality, even w/ this poopy INTerlace thing going on.
* DVD is INTerlaced and/or PROGressive

>> That's why ripped DVDs are much better encoded then own >> camcorder captures?!
Well, really its because their's vertually NO noise in the orig
Film-to-DVD conversion or encode from prof. studios process.

>> So without breaking the SVCD standard I won't be able to get >> better quality?
Till you learn how to "hold" and "move" your "DV Cam" properly,
you wont be seeing any great looking SVCD encodes (i've a few)
AND, lighting source is also VERY IMPORTANT. Don't keep zooming
in and out. and try NOT to move/jerk your cam in your hand.
Learn how to balance your cam in your hand while you shoot
I left my DV cam on my tripod while I took a video of my 55 gal
fish tank. The result, great looking svcd, but still not
comparatable to DVD, but very good quality, non-the-less

Again, the quality from DVD is due to "no noise" which causes
the blocks and artifacs you see (ie, in YOUR encodes)

>> BTW - I have the TRV900 too - and a tripod.
>> The whole things sounds very unsatisfiying...
* What's your lighting source??
* Do you see a lot of "grainy" or "sandy" like quality in your
videos when you play them back to TV via your CAM??

You can visit my sample website, soon as I get it straigten out.
I have samples I've done with my DV cam, Canon ZR-10
* no passthrough. Encodes are from pre-recorded satalete to
miniDV tapes.
* will post my link when I get the chance.

I've posted a sample clip I did w/ my DV cam, Canon ZR-10, please let me
know what you guys think of it

Thanks for your support all.
-vhelp
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VHELP's revised website of sample(s) <<HERE>>