A question on video quality loss

[Brian]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

I'm told that when I capture video from my DV camera to the hard
drive, cut out certain scenes then save back to my DV camera then
there is no loss in video quality. I should be able to do this 5 or 50
times with no video loss.
What I don't understand is that if the video is compressed 5 times (I
read that a AVI DV codec will compress the video signal) each time I
copy the video to my hard drive using a AVI DV codec then there must
be some loss of video quality.

Can someone help me to understand why there is no loss in the video
quality?

Regards Brian

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

There is some loss because it won't be exact. The lost is so little
that it's considered no lost you don't make any changes. What you're doing
is virutally copying the content from your DV camera through the firewire
alomst as if you were using an external hard drive to copy the content from
a hard drive. You're not changing the codec. The codec is already there in
the camera. If you don't modify it at all, you're putting the same codec
back into the camera. It retains the same compression all the time.

If you uncompressed it (for some reason) then recompressed it, then
there would be even more lost.

-- L. James


-----------------------
L. D. James
ljames@apollo3.com
www.apollo3.com/~ljames


"Brian" <bclark@es.co.nz> wrote in message
news:jn72e0l5cjmubbibasnv6gef9jlmn5rg3t@4ax.com...
> I'm told that when I capture video from my DV camera to the hard
> drive, cut out certain scenes then save back to my DV camera then
> there is no loss in video quality. I should be able to do this 5 or 50
> times with no video loss.
> What I don't understand is that if the video is compressed 5 times (I
> read that a AVI DV codec will compress the video signal) each time I
> copy the video to my hard drive using a AVI DV codec then there must
> be some loss of video quality.
>
> Can someone help me to understand why there is no loss in the video
> quality?
>
> Regards Brian

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

Brian wrote:
> I'm told that when I capture video from my DV camera to the hard
> drive, cut out certain scenes then save back to my DV camera then
> there is no loss in video quality. I should be able to do this 5 or 50
> times with no video loss.
> What I don't understand is that if the video is compressed 5 times (I
> read that a AVI DV codec will compress the video signal) each time I
> copy the video to my hard drive using a AVI DV codec then there must
> be some loss of video quality.
>
> Can someone help me to understand why there is no loss in the video
> quality?
>
> Regards Brian


Both replies so far have said that there will be a quality loss doing what
Brian wants to do - and they are wrong. This isn't the analog days where
you suffered generation loss when making copies. There will be no quality
loss as it's a straight digital transfer in and out - no further compression
is used.
The only time image quality "might" take a hit is doing any kind of effect
(dissolve/wipe, etc.). I say "might" because it depends on the codec being
used. Some are much better than others.

Mike

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"Brian" wrote ...
> I'm told that when I capture video from my DV camera to
> the hard drive, cut out certain scenes then save back to my
> DV camera then there is no loss in video quality.

That is correct. (Assuming that your software activities aren't
trying to decode and re-encode the video, i.e. "render") If you
add any titles, special effects, dissolves, etc, then the video must
be rendered. Most software does NOT re-render when you are
only doing straight cuts.

> I should be able to do this 5 or 50 times with no video loss.

Theoretically.

> What I don't understand is that if the video is compressed 5
> times (I read that a AVI DV codec will compress the video
> signal)

You read wrong. I've never heard of an AVI DV codec that
does *any* compression. The DV bitstream was compressed
5:1 when it was originally converted from analog to digital
in the camcorder. No further compression takes place in any
DV codec.

> each time I copy the video to my hard drive using a AVI DV
> codec then there must be some loss of video quality.

If the AVI DV codec actually performed additional compression,
then that would be a likely situation. But no AVI DV codec
does any additional compression.

The DV signal itself was compressed 5:1 in the camcorder.
Once it is recorded as ones and zeroes on the tape, exporting
it via Firewire, recording into AVI files, exporting via Firewire,
and re-recording it back to tape encounters no additional compression.
>
> Can someone help me to understand why there is no loss in the video
> quality?

Because the AVI DV coded does *NOT* perform any additional
compression.

 

[Rich]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"Brian" <bclark@es.co.nz> wrote in message
news:jn72e0l5cjmubbibasnv6gef9jlmn5rg3t@4ax.com...
> I'm told that when I capture video from my DV camera to the hard
> drive, cut out certain scenes then save back to my DV camera then
> there is no loss in video quality. I should be able to do this 5 or 50
> times with no video loss.
> What I don't understand is that if the video is compressed 5 times (I
> read that a AVI DV codec will compress the video signal) each time I
> copy the video to my hard drive using a AVI DV codec then there must
> be some loss of video quality.
>
> Can someone help me to understand why there is no loss in the video
> quality?
>
> Regards Brian

Brian, I have done the above and have not noticed any visible differences in
the video (or audio), but there is a difference, in file size. I just
imported into an editor (Movie Maker) a small test file, test_0000.avi,
saved it as DV-AVI, then imported that one and saved, etc. Each test file
got a bit smaller (see below) but I can not see or hear any differences
playing them back on my computer. I may import a resolution chart later
(some day permitting) and look at some frames to see if their is any
observable difference. I also read both files into a text editor which can
compare binary files (Text Pad) and the differences appear to be scattered
throughout the file (Not just at the beginning or end as I expected).


test_0000.avi 25,215,488
test_0001.avi 25,095,168
test_0002.avi 24,974,848
test_0003.avi 24,854,528

So I now wonder if I continued when would the file size stop decreasing, or
what does this all mean.

Rich

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

Mike, I was very hopeful in this 100% lossless environment, as I had
read the same definition that you're giving. I was told transferring though
the firewire was much like transferring date between hard drives with no
loss. I tested this by doing a transfer back and forth. The resulting
files are different. This difference, I interpret as being a loss. I'm
sure the lose is very minute, but the difference is there. Maybe it will
take 500 or more generations before the differences become noticeable to
this eye. I didn't run the test for more than a couple of generations.

If I copied the video between two hard drives, the resulting files
would never be different (unless I had a system malfunction). Because the
files would continue to be identical, this would be absolutely lossless.

-- L. James

-----------------------
L. D. James
ljames@apollo3.com
www.apollo3.com/~ljames


"Mike Kujbida" <kujfam-misleadingspam@sympatico.ca> wrote in message
news:2kcv8rFqpdaU1@uni-berlin.de...
> Brian wrote:
> > I'm told that when I capture video from my DV camera to the hard
> > drive, cut out certain scenes then save back to my DV camera then
> > there is no loss in video quality. I should be able to do this 5 or 50
> > times with no video loss.
> > What I don't understand is that if the video is compressed 5 times (I
> > read that a AVI DV codec will compress the video signal) each time I
> > copy the video to my hard drive using a AVI DV codec then there must
> > be some loss of video quality.
> >
> > Can someone help me to understand why there is no loss in the video
> > quality?
> >
> > Regards Brian
>
>
> Both replies so far have said that there will be a quality loss doing what
> Brian wants to do - and they are wrong. This isn't the analog days where
> you suffered generation loss when making copies. There will be no quality
> loss as it's a straight digital transfer in and out - no further
compression
> is used.
> The only time image quality "might" take a hit is doing any kind of effect
> (dissolve/wipe, etc.). I say "might" because it depends on the codec
being
> used. Some are much better than others.
>
> Mike
>

 

[Rio]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

> Both replies so far have said that there will be a quality loss doing what
> Brian wants to do - and they are wrong. This isn't the analog days where
> you suffered generation loss when making copies. There will be no quality
> loss as it's a straight digital transfer in and out - no further
compression
> is used.
> The only time image quality "might" take a hit is doing any kind of effect
> (dissolve/wipe, etc.). I say "might" because it depends on the codec
being
> used. Some are much better than others.


As far as I know DV isn't lossless, it's a lossy format so the copy from/to
camera via firewire IS a copy without encoding, so it is lossless, but also
reencoding it to DV format means loosing something.
Try not to add any transition and encode/decode from/to DV Video lot of
times and you'll see that it looses quality.

--
rIO.sK

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"Rich" <richsanchez43@usa.com> wrote in message
news:btgEc.17828$w07.7626@newsread2.news.pas.earthlink.net...

> test_0000.avi 25,215,488
> test_0001.avi 25,095,168
> test_0002.avi 24,974,848
> test_0003.avi 24,854,528

Just out of interest have you tried opening the DV file in a programme like
virtualdub and going to "file information" to see if the number of frames in
the file stays the same?

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

Richard Crowley wrote:
> snip <
> You read wrong. I've never heard of an AVI DV codec that
> does *any* compression. The DV bitstream was compressed
> 5:1 when it was originally converted from analog to digital
> in the camcorder. No further compression takes place in any
> DV codec.


Richard, the only gotcha here is whether the codec uses a luminance range of
16-235 or 0-255. For example, the Microsoft DV codec is 16-235 while the
Vegas DV codec is 0-255. If you bring a Microsoft-encoded file into Vegas,
it will stretch it back out which will cause some degredation. As long as
you stick to one style, you're (hopefully) OK.
JVC had a tutorial on the whole set-up issue (which this essentially is) at
http://pro.jvc.com/pro/attributes/prodv/clips/blacksetup/JVC_DEMO.swf
Adam Wilt also discusses this issue at
http://www.adamwilt.com/DV-FAQ-editing.html#CodecProblems

Mike

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"L. D. James" wrote ...
> Mike, I was very hopeful in this 100% lossless environment,
> as I had read the same definition that you're giving. I was told
> transferring though the firewire was much like transferring data
> between hard drives with no loss. I tested this by doing a transfer
> back and forth. The resulting files are different. This difference,
> I interpret as being a loss.

I believe you are misinterpereting your evidence. Even if the
bitstreams are identical (which I believe they are), the difference
can be completely accounted for in the imprecision of the
selection of starting and stopping points in the tape medium.
If there were a single frame more or less captured, the file
would appear to be completely different by data analysis
methods, but identical to our eyes.

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"Mike Kujbida" <kujfam-misleadingspam@sympatico.ca> wrote in message
news:2ke4lhF1a1prU1@uni-berlin.de...
> Richard Crowley wrote:
> > snip <
> > You read wrong. I've never heard of an AVI DV codec that
> > does *any* compression. The DV bitstream was compressed
> > 5:1 when it was originally converted from analog to digital
> > in the camcorder. No further compression takes place in any
> > DV codec.
>
>
> Richard, the only gotcha here is whether the codec uses a luminance range
of
> 16-235 or 0-255. For example, the Microsoft DV codec is 16-235 while the
> Vegas DV codec is 0-255. If you bring a Microsoft-encoded file into
Vegas,
> it will stretch it back out which will cause some degredation. As long as
> you stick to one style, you're (hopefully) OK.
> JVC had a tutorial on the whole set-up issue (which this essentially is)
at
> http://pro.jvc.com/pro/attributes/prodv/clips/blacksetup/JVC_DEMO.swf
> Adam Wilt also discusses this issue at
> http://www.adamwilt.com/DV-FAQ-editing.html#CodecProblems

But is that even an issue with straight dubbing or cuts-only
assembly? There is no requirement to decode/encode the video.

 

[Rich]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"Adrian Boliston" <adrian@boliston.co.uk> wrote in message
news:2kdraqF17m4lU1@uni-berlin.de...
> "Rich" <richsanchez43@usa.com> wrote in message
> news:btgEc.17828$w07.7626@newsread2.news.pas.earthlink.net...
>
> > test_0000.avi 25,215,488
> > test_0001.avi 25,095,168
> > test_0002.avi 24,974,848
> > test_0003.avi 24,854,528
>
> Just out of interest have you tried opening the DV file in a programme
like
> virtualdub and going to "file information" to see if the number of frames
in
> the file stays the same?
>
>

I just did now
test_0000.avi 209 frames
test_0001.avi 208 frames
test_0002.avi 207 frames
test_0003.avi 206 frames

Rich

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

dv avis have compression , so the more you play with it , retouch and then
save, each time you can expect some more compression, some people in this
group, suggest compression can be quite noticeable, after a few times,
try and play your dv through windows media player ,
play it 100% size, then play it at full screen, this will give you an
indication.

"Brian" <bclark@es.co.nz> wrote in message
news:jn72e0l5cjmubbibasnv6gef9jlmn5rg3t@4ax.com...
> I'm told that when I capture video from my DV camera to the hard
> drive, cut out certain scenes then save back to my DV camera then
> there is no loss in video quality. I should be able to do this 5 or 50
> times with no video loss.
> What I don't understand is that if the video is compressed 5 times (I
> read that a AVI DV codec will compress the video signal) each time I
> copy the video to my hard drive using a AVI DV codec then there must
> be some loss of video quality.
>
> Can someone help me to understand why there is no loss in the video
> quality?
>
> Regards Brian

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

dv codec has compression .....
compression = quality loss
it is not uncompressed ....

"Mike Kujbida" <kujfam-misleadingspam@sympatico.ca> wrote in message
news:2kcv8rFqpdaU1@uni-berlin.de...
> Brian wrote:
> > I'm told that when I capture video from my DV camera to the hard
> > drive, cut out certain scenes then save back to my DV camera then
> > there is no loss in video quality. I should be able to do this 5 or 50
> > times with no video loss.
> > What I don't understand is that if the video is compressed 5 times (I
> > read that a AVI DV codec will compress the video signal) each time I
> > copy the video to my hard drive using a AVI DV codec then there must
> > be some loss of video quality.
> >
> > Can someone help me to understand why there is no loss in the video
> > quality?
> >
> > Regards Brian
>
>
> Both replies so far have said that there will be a quality loss doing what
> Brian wants to do - and they are wrong. This isn't the analog days where
> you suffered generation loss when making copies. There will be no quality
> loss as it's a straight digital transfer in and out - no further
compression
> is used.
> The only time image quality "might" take a hit is doing any kind of effect
> (dissolve/wipe, etc.). I say "might" because it depends on the codec
being
> used. Some are much better than others.
>
> Mike
>

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

Jeremy Wrinklebottom wrote:
> dv codec has compression .....
> compression = quality loss
> it is not uncompressed ....

If ALL he's doing is removing selected pieces of his clips, there is no
compression, therefore NO quality loss.


Mike


>
> "Mike Kujbida" <kujfam-misleadingspam@sympatico.ca> wrote in message
> news:2kcv8rFqpdaU1@uni-berlin.de...
>> Brian wrote:
>>> I'm told that when I capture video from my DV camera to the hard
>>> drive, cut out certain scenes then save back to my DV camera then
>>> there is no loss in video quality. I should be able to do this 5 or
>>> 50 times with no video loss.
>>> What I don't understand is that if the video is compressed 5 times
>>> (I read that a AVI DV codec will compress the video signal) each
>>> time I copy the video to my hard drive using a AVI DV codec then
>>> there must be some loss of video quality.
>>>
>>> Can someone help me to understand why there is no loss in the video
>>> quality?
>>>
>>> Regards Brian
>>
>>
>> Both replies so far have said that there will be a quality loss
>> doing what Brian wants to do - and they are wrong. This isn't the
>> analog days where you suffered generation loss when making copies.
>> There will be no quality loss as it's a straight digital transfer in
>> and out - no further compression is used.
>> The only time image quality "might" take a hit is doing any kind of
>> effect (dissolve/wipe, etc.). I say "might" because it depends on
>> the codec being used. Some are much better than others.
>>
>> Mike

 

[Brian]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"L. D. James" <ljames@apollo3.com> wrote:

> There is some loss because it won't be exact. The lost is so little
>that it's considered no lost you don't make any changes. What you're doing
>is virutally copying the content from your DV camera through the firewire
>alomst as if you were using an external hard drive to copy the content from
>a hard drive. You're not changing the codec. The codec is already there in
>the camera. If you don't modify it at all, you're putting the same codec
>back into the camera. It retains the same compression all the time.
>
> If you uncompressed it (for some reason) then recompressed it, then
>there would be even more lost.
>
> -- L. James
>
>
>-----------------------
>L. D. James
>ljames@apollo3.com
>www.apollo3.com/~ljames
>
>
>"Brian" <bclark@es.co.nz> wrote in message
>news:jn72e0l5cjmubbibasnv6gef9jlmn5rg3t@4ax.com...
>> I'm told that when I capture video from my DV camera to the hard
>> drive, cut out certain scenes then save back to my DV camera then
>> there is no loss in video quality. I should be able to do this 5 or 50
>> times with no video loss.
>> What I don't understand is that if the video is compressed 5 times (I
>> read that a AVI DV codec will compress the video signal) each time I
>> copy the video to my hard drive using a AVI DV codec then there must
>> be some loss of video quality.
>>
>> Can someone help me to understand why there is no loss in the video
>> quality?
>>
>> Regards Brian

Thanks L.James and others for your replies.
If I were to load the video in a video editor and remove some of the
video content then saved it back to the DV camera would I still have
no video quality loss?

This is useful to know as often I want to find and delete bad bits of
my video then record it back to the camera until I'm ready to do the
final editing.

Regards Brian

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

Brian. According to the firewire definition, it would be lossless.
According to my analysis, there would be no real detectable loss. I'm sure
you could do it 50 times and still not notice any quality lost, as long as
you didn't add transitions or effects (modify the video). This would have
uncompressed and recompressed the video. Otherwise it would never have been
uncompressed. If you added effect or transitions, only the parts with the
effects and transitions would have loss.

To do as you described below, there would be virtually no quality loss.

-- L.
James

"Brian" <bclark@es.co.nz> wrote in message
news:3oi2e05cf5qml44dv2e6dh72622ior2mps@4ax.com...
> "L. D. James" <ljames@apollo3.com> wrote:
>
> > There is some loss because it won't be exact. The lost is so little
> >that it's considered no lost you don't make any changes. What you're
doing
> >is virutally copying the content from your DV camera through the firewire
> >alomst as if you were using an external hard drive to copy the content
from
> >a hard drive. You're not changing the codec. The codec is already there
in
> >the camera. If you don't modify it at all, you're putting the same codec
> >back into the camera. It retains the same compression all the time.
> >
> > If you uncompressed it (for some reason) then recompressed it, then
> >there would be even more lost.
> >
> > -- L. James
> >
> >
> >-----------------------
> >L. D. James
> >ljames@apollo3.com
> >www.apollo3.com/~ljames
> >
> >
> >"Brian" <bclark@es.co.nz> wrote in message
> >news:jn72e0l5cjmubbibasnv6gef9jlmn5rg3t@4ax.com...
> >> I'm told that when I capture video from my DV camera to the hard
> >> drive, cut out certain scenes then save back to my DV camera then
> >> there is no loss in video quality. I should be able to do this 5 or 50
> >> times with no video loss.
> >> What I don't understand is that if the video is compressed 5 times (I
> >> read that a AVI DV codec will compress the video signal) each time I
> >> copy the video to my hard drive using a AVI DV codec then there must
> >> be some loss of video quality.
> >>
> >> Can someone help me to understand why there is no loss in the video
> >> quality?
> >>
> >> Regards Brian
>
> Thanks L.James and others for your replies.
> If I were to load the video in a video editor and remove some of the
> video content then saved it back to the DV camera would I still have
> no video quality loss?
>
> This is useful to know as often I want to find and delete bad bits of
> my video then record it back to the camera until I'm ready to do the
> final editing.
>
> Regards Brian
>

-----------------------
L. D. James
ljames@apollo3.com
www.apollo3.com/~ljames

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

"Brian" wrote ...
> If I were to load the video in a video editor and remove
> some of the video content then saved it back to the DV
> camera would I still have no video quality loss?

Correct.

> This is useful to know as often I want to find and delete
> bad bits of my video then record it back to the camera
> until I'm ready to do the final editing.

You must be using overpriced tape if doing all that work
(and risking something going wrong) is worth less than a
DV tape!

Note further that with hard drive capacities increasing and
prices dropping, in many cases it is cheaper to leave the
video on a plug-in hard drive than to write it back to tape.

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

Richard Crowley wrote:
> "Mike Kujbida" <kujfam-misleadingspam@sympatico.ca> wrote in message
> news:2ke4lhF1a1prU1@uni-berlin.de...
>> Richard Crowley wrote:
>>> snip <
>>> You read wrong. I've never heard of an AVI DV codec that
>>> does *any* compression. The DV bitstream was compressed
>>> 5:1 when it was originally converted from analog to digital
>>> in the camcorder. No further compression takes place in any
>>> DV codec.
>>
>>
>> Richard, the only gotcha here is whether the codec uses a luminance
>> range of 16-235 or 0-255. For example, the Microsoft DV codec is
>> 16-235 while the Vegas DV codec is 0-255. If you bring a
>> Microsoft-encoded file into Vegas, it will stretch it back out which
>> will cause some degredation. As long as you stick to one style,
>> you're (hopefully) OK.
>> JVC had a tutorial on the whole set-up issue (which this essentially
>> is) at
>> http://pro.jvc.com/pro/attributes/prodv/clips/blacksetup/JVC_DEMO.swf
>> Adam Wilt also discusses this issue at
>> http://www.adamwilt.com/DV-FAQ-editing.html#CodecProblems
>
> But is that even an issue with straight dubbing or cuts-only
> assembly? There is no requirement to decode/encode the video.


It's my understanding (please correct me if I'm wrong) that, as long as you
use the program that created the file in the first place, you won't have any
problems. It's when you do as I mentioned above (create in MovieMaker -
import/export with Vegas - re-import back into MovieMaker) that you'll run
into problems. And don't say no one would ever knowingly do that. At the
college I work at, we have students who only have MovieMaker at home and we
only have Vegas in the edit suites so it happens with us quite a bit. You
will see degradation if they do more than one transfer back and forth, even
if it's straight cuts :-(

Mike

 

[Guest]

Archived from groups: rec.video.desktop,alt.video.dvd.software (More info?)

I agree. if you are making simple cuts, there should be absolutely no change in
the video as long as the DV video settings remain the same and you choose not to
"always recompress" video. Even the stuff you change with transitions and other
effects should look virtually the same as the original DV. This is provided you
import and export the video via with Firewire, which isn't really "capturing"
video, but more like transferring digital data.

Where people run into trouble is if they use something like Windows Movie Maker
and just choose the default settings. This will convert the video to another
format and totally lose the quality. You need to keep the video in full DV
format every step of the editing process.

"Mike Kujbida" <kujfam-misleadingspam@sympatico.ca> wrote in message
news:2kcv8rFqpdaU1@uni-berlin.de...
> Brian wrote:
> > I'm told that when I capture video from my DV camera to the hard
> > drive, cut out certain scenes then save back to my DV camera then
> > there is no loss in video quality. I should be able to do this 5 or 50
> > times with no video loss.
> > What I don't understand is that if the video is compressed 5 times (I
> > read that a AVI DV codec will compress the video signal) each time I
> > copy the video to my hard drive using a AVI DV codec then there must
> > be some loss of video quality.
> >
> > Can someone help me to understand why there is no loss in the video
> > quality?
> >
> > Regards Brian
>
>
> Both replies so far have said that there will be a quality loss doing what
> Brian wants to do - and they are wrong. This isn't the analog days where
> you suffered generation loss when making copies. There will be no quality
> loss as it's a straight digital transfer in and out - no further compression
> is used.
> The only time image quality "might" take a hit is doing any kind of effect
> (dissolve/wipe, etc.). I say "might" because it depends on the codec being
> used. Some are much better than others.
>
> Mike
>