A question on video quality loss

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
19 answers Last reply
More about question video quality loss
  1. 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
  2. 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
  3. 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.
  4. 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
  5. 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
    >
  6. 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
  7. 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?
  8. 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
  9. 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.
  10. 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.
  11. 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
  12. 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
  13. 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
    >
  14. 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
  15. 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
  16. 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
  17. 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.
  18. 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
  19. 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
    >
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