Archived from groups: rec.video.desktop,rec.video.production (More info?)

Where could you go to try and fathom the subject of Codecs - the how's and
why's of them regarding video, compression, decompression, recompression
etc. etc. I feel like I"m stumbling around half blind working with computer
video not really understanding these issues.

Thanks for all input

Archived from groups: rec.video.desktop,rec.video.production (More info?)

"Doc" wrote ...
> Where could you go to try and fathom the subject of Codecs -
> the how's and why's of them regarding video, compression,
> decompression, recompression etc. etc. I feel like I"m stumbling
> around half blind working with computer video not really
> understanding these issues.

http://www.fourcc.org has one of the more comprehensive listings
of codecs and their ID numbers. But not sure exactly what info you
are looking for?

Are you having some sort of problem that you think implicates
codecs? Lots of us work in video for years without giving codecs
a second thought. They are mostly installed and invoked completely
automatically.

Perhaps you could try specific questions that would reveal where
you are coming from?

Archived from groups: rec.video.desktop,rec.video.production (More info?)

In a nutshell codecs are a way of sharing video files. Codecs are an
algorithm for encoding the video frames interleaved with audio. AVI stands
for Audio Video Interleave. The format AVI is a container in which this
encoded video information is stored, as is the MOV format. Some codecs are
hardware based, some are software based and some are both hardware/software
based. Many of the original capture cards for the Windows OS such as the
Intel Personal Video Recorder, were based on a Brooktree encoder chip for
video capture. The video could be played back on other Windows systems using
the Intel Indeo software codec. The Intel Indeo codec is and has always been
able to also write the video information to both the AVI & MOV containers,
as are other software based codecs such as Cinepak.

The data rate of a video file governs the abiltiy of the target device for
playback. Originally CD drives were only 1X and the data rate for video
files had to fall into the limitations of that device for playback. In order
to reach the planned target some concessions had to be made to allow smooth
playback, i.e. smaller frame resolutions, lower frame rates, lower audio
rates. This is where compression comes into play - all these factors
gathered together and crammed into a single stream for playback at the
lowered target data rate.

Compression has always had a lot to do with the ability to share video over
various connection speeds through the internet. Full frame resolution NTSC
video with CD quality audio uncompressed has a data rate of nearly 30MB per
second. Even with large amounts of compression that stream would choke over
a 56K connection. Over the years many different types of codecs have been
developed in the hope of achieving better quality video at lower data rates.
This is where MPEG-2 compression outshines all the rest lowering the
Megabytes to megabits and still offering a high quality picture with sound.
Unlike many of the non-DV video algorithm's MPEG-2 does not have sub-format
frame ratio's - which I cover in the next paragraph.

Understanding codecs and compression/decompression is really not that
difficult in obvious information - more compression less picture quality,
less compression better picture quality. It is more difficult to understand
how to compress the video in order to achieve the target playback you
desire. And in truth practice makes perfect. There is always a trade-off
when it comes to passing video over the web, particularly when the users
have 56K or lower connections. Unless the user has broadband the image has
to suffer in some way. It has to be compressed to lower data rates and frame
rates are cut down to 10 or 15fps.

Most video applications using software based codecs assume a 4:3 ratio and
the sub-ratio's based upon it, i.e. 640x480, 320x240, 160x120,etc. all
square pixel ratio's. This is because DV was not around and analog capture
was done in square pixel 4:3 screen ratio's. MPEG-2 on the other hand
expects the DV pixel ratio and frame resolution. There is a breaking point
with any codec in relationship to compression - the more the compression the
lesser the picture quality. Natually the less the compression the better the
picture quality.

Take a look at this video file on my website.
http://digitalvideosolutions.com/video/Top_Flight.wmv I compressed it with
the broadband user in mind. The frame resolution is interlaced 720x480 with
a pixel ratio of D1/DV NTSC (0.9) the audio is 44kHz and the frame rate is a
full 29.97fps. The file is only 18.5 seconds long. I used Windows Media
Encoder 9 choosing to keep frame rate, etc. high under the settings of a 2MB
broadband connection. The file size is 4MB. You could probably do better
using DivX but still, at it's present compression level it is about 18 times
smaller than the original DV file which was around 114MB.

Your target is the determining factor to compression. With higher data rates
all the software codecs loaded on your Windows system will yield a very nice
picture. I really don't know what more one can tell you in regard to codecs
that would make it any easier to know what you end result will be. If you
are looking for single data rate video with good quality and wide spread
cross platform playback then MPEG-1 may be the answer you are looking for.
Take a look at this short MPEG-1 file
http://digitalvideosolutions.com/video/Wed02.mpeg Even when played back at
200% the frame size it really doesn't look too bad, and it's just the normal
MPEG-1 VCD compression level. I hope this helps in some way. I am sure there
are others with still more pertinent advice or information which I may have
overlooked or mis-quoted as fact.
--
Larry Johnson
Digital Video Solutions
webmaster@digitalvideosolutions.com
http://www.digitalvideosolutions.com
877-227-6281 Toll Free Sales Assistance
386-672-1941 Customer Service
386-672-1907 Technical Support
386-676-1515 Fax


"Doc" <docsavage20@xhotmail.com> wrote in message
news:E82Cd.12073$qf5.633@newsread3.news.atl.earthlink.net...
> Where could you go to try and fathom the subject of Codecs - the how's
and
> why's of them regarding video, compression, decompression, recompression
> etc. etc. I feel like I"m stumbling around half blind working with
computer
> video not really understanding these issues.
>
> Thanks for all input
>
>

Archived from groups: rec.video.desktop,rec.video.production (More info?)

"Wilbert Dijkhof" wrote ...
>
> Digital Video Solutions wrote:
>>
>> In a nutshell codecs are a way of sharing video files. Codecs are an
>> algorithm for encoding the video frames interleaved with audio. AVI
>> stands
>
> No, they are not. There are video codecs which compress/decomprocess
> video, and you have audio codecs which compress/decomprocess audio.

Actually, most video codecs include the audio stream since
most of us have become accustomed to "talkies", at least in
the last 100 years or so.

>> for Audio Video Interleave. The format AVI is a container in which
>> this
>> encoded video information is stored, as is the MOV format. Some
>> codecs are
>
> Ok. Note there are more containers (OGM, MKV, etc ...).
>
>> hardware based, some are software based and some are both
>> hardware/software
>
> Just curious. Could you give some examples of hardware codecs?

Every DV camcorder on this planet has a hardware DV codec. Even
codecs used for computer processing of video (like Indeo) were done
in hardware before CPUs were fast enough to do it in software.

>> based. Many of the original capture cards for the Windows OS such as
>> the
>> Intel Personal Video Recorder, were based on a Brooktree encoder chip
>> for
>
> You mean capture chip? Those don't encode anything, they just capture.

Many of them encode/decode as well. For example you can
buy high-end video capture/edit systems that include hardware
encode/decode (aka. "accellerator" ) boards.
>
>> video capture. The video could be played back on other Windows
>> systems using
>> the Intel Indeo software codec. The Intel Indeo codec is and has
>> always been
>> able to also write the video information to both the AVI & MOV
>> containers,
>> as are other software based codecs such as Cinepak.
>>
>> The data rate of a video file governs the abiltiy of the target
>> device for
>> playback. Originally CD drives were only 1X and the data rate for
>> video
>> files had to fall into the limitations of that device for playback.
>> In order
>> to reach the planned target some concessions had to be made to allow
>> smooth
>> playback, i.e. smaller frame resolutions, lower frame rates, lower
>> audio
>> rates. This is where compression comes into play - all these factors
>> gathered together and crammed into a single stream for playback at
>> the
>> lowered target data rate.
>
> Compression has nothing to do with frame sizes or frame rates. It has
> to do with smoothing details out.

Compression has everything to do with frame sizes/rates.
It enables us to preserve the desired size/rate with less
overhead of bitstream volume.

Archived from groups: rec.video.desktop, rec.video.production (More info?)

Richard Crowley wrote:
> "Wilbert Dijkhof" wrote ...
> >
> > Digital Video Solutions wrote:
> >>
> >> In a nutshell codecs are a way of sharing video files. Codecs are
an
> >> algorithm for encoding the video frames interleaved with audio.
AVI
> >> stands
> >
> > No, they are not. There are video codecs which
compress/decomprocess
> > video, and you have audio codecs which compress/decomprocess audio.
>
> Actually, most video codecs include the audio stream since
> most of us have become accustomed to "talkies", at least in
> the last 100 years or so.
>
> >> for Audio Video Interleave. The format AVI is a container in which

> >> this
> >> encoded video information is stored, as is the MOV format. Some
> >> codecs are
> >
> > Ok. Note there are more containers (OGM, MKV, etc ...).
> >
> >> hardware based, some are software based and some are both
> >> hardware/software
> >
> > Just curious. Could you give some examples of hardware codecs?
>
> Every DV camcorder on this planet has a hardware DV codec. Even
> codecs used for computer processing of video (like Indeo) were done
> in hardware before CPUs were fast enough to do it in software.
>
> >> based. Many of the original capture cards for the Windows OS such
as
> >> the
> >> Intel Personal Video Recorder, were based on a Brooktree encoder
chip
> >> for
> >
> > You mean capture chip? Those don't encode anything, they just
capture.
>
> Many of them encode/decode as well. For example you can
> buy high-end video capture/edit systems that include hardware
> encode/decode (aka. "accellerator" ) boards.
> >
> >> video capture. The video could be played back on other Windows
> >> systems using
> >> the Intel Indeo software codec. The Intel Indeo codec is and has
> >> always been
> >> able to also write the video information to both the AVI & MOV
> >> containers,
> >> as are other software based codecs such as Cinepak.
> >>
> >> The data rate of a video file governs the abiltiy of the target
> >> device for
> >> playback. Originally CD drives were only 1X and the data rate for
> >> video
> >> files had to fall into the limitations of that device for
playback.
> >> In order
> >> to reach the planned target some concessions had to be made to
allow
> >> smooth
> >> playback, i.e. smaller frame resolutions, lower frame rates, lower

> >> audio
> >> rates. This is where compression comes into play - all these
factors
> >> gathered together and crammed into a single stream for playback at

> >> the
> >> lowered target data rate.
> >
> > Compression has nothing to do with frame sizes or frame rates. It
has
> > to do with smoothing details out.
>
> Compression has everything to do with frame sizes/rates.
> It enables us to preserve the desired size/rate with less
> overhead of bitstream volume.

Hi,

CODEC stands for COmpressor / DEcompressor

Each codec has a different method (generalization for simplicity) of
compressing the video or audio data contained in a movie.

Since the audio and video are seperate streams you may use one video
codec and one audio codec to compress a file.

Different codecs may provide higher quality or smaller size. Some
codecs can be choosen to give you a specific transfer rate. e.g
streaming video, select a window size and codec to provide say 36K
rates for a dialup link.

To try some of these things take a 30 second clip.
output it using the same frame size, use different codecs and quality
settings. Compare the file sizes and quality on playback. Then look at
the statistics (if your player provides them ) for the transfer rates
involved.

There are a number of sites that list codec names and the fourcc code.
These are useful if you have a video (or audio) that will not play. You
can extract the fourcc code and look it up.

I have not found any good sites that discuss the available codecs and
compare the benefits of each.

For preparing video for DVD production the supplied codecs with
whatever software you are using are probably good enough.

For web site video look at DIVX or XVID - they seem to have high
compression rates with good quality.

Compression and decompression routines are often implemented in
hardware. Benefit is they run very fast without loading the processor.
Against that is the fact that you cannot easily change the compression
routine as standards change. MPEG is often in hardware on better
capture cards.

Archived from groups: rec.video.desktop,rec.video.production (More info?)

Richard Crowley wrote:
>
> "Wilbert Dijkhof" wrote ...
> >
> > Digital Video Solutions wrote:
> >>
> >> In a nutshell codecs are a way of sharing video files. Codecs are an
> >> algorithm for encoding the video frames interleaved with audio. AVI
> >> stands
> >
> > No, they are not. There are video codecs which compress/decomprocess
> > video, and you have audio codecs which compress/decomprocess audio.
>
> Actually, most video codecs include the audio stream since
> most of us have become accustomed to "talkies", at least in
> the last 100 years or so.

I don't know how you define most, but you can't encode the audio with
the xvid, divx, 3ivx and many avc encoders.

> >> based. Many of the original capture cards for the Windows OS such as
> >> the
> >> Intel Personal Video Recorder, were based on a Brooktree encoder chip
> >> for
> >
> > You mean capture chip? Those don't encode anything, they just capture.
>
> Many of them encode/decode as well. For example you can
> buy high-end video capture/edit systems that include hardware
> encode/decode (aka. "accellerator" ) boards.

Yes, you are right of course.

> >> In order
> >> to reach the planned target some concessions had to be made to allow
> >> smooth
> >> playback, i.e. smaller frame resolutions, lower frame rates, lower
> >> audio
> >> rates. This is where compression comes into play - all these factors
> >> gathered together and crammed into a single stream for playback at
> >> the
> >> lowered target data rate.
> >
> > Compression has nothing to do with frame sizes or frame rates. It has
> > to do with smoothing details out.
>
> Compression has everything to do with frame sizes/rates.
> It enables us to preserve the desired size/rate with less
> overhead of bitstream volume.

Yes, of course. The lower the frame size you choose the more you
can compress. Perhaps I should formulate it differently 'compression
itself is not about frame sizes or frame rates'. You can perfectly
apply compression without distorting the quality too much and without
reducing frame size or frame rate.

Of course if you just lower the frame rate you are not compressing
at all.

Wilbert

Archived from groups: rec.video.desktop,rec.video.production (More info?)

Digital Video Solutions wrote:
> *Well Wilbert, for someone who "hangs around at the video forums (doom9
> for example)" it appears that you really don't have a firm grasp on
> video compression, video resolutions, frame rates or the structure of
> competitent video analysis whatsoever. When you can stop "hanging around
> these cool video forums" and grab a set of clients who are actually
> doing something in the real world of video you can tell everyone how
> frame resolutions, frame rates, data rates and bitrates have nothing to
> do with compression.*

It never ceases to amaze me the vigor with which ignorance is
promulgated online. Having been in professional video since 1968, and
having spent most of my time in hardware and software design for the
video industry, it is impressive to see someone like Wilbert make such
pronouncements that are filled with so much misinformation. Clearly, he
seems convinced that video was born about the time of the desktop
computer <g>.

My hat's off to you for setting min straight in a number of areas. I
generally don't take the time, because (as you may see later) his ilk
all too often come back with more of the same, and proceed to waste time
and bandwidth, apparently in the belief that loud screams will overcome
logic and knowledge.

Bill

Archived from groups: rec.video.desktop,rec.video.production (More info?)

Thank you, Bill. I would normally not have taken so much time in answering
someone like Wilbert, save for the fact there are many out there who may
take his words to heart and be misled.

"William Meyer" <wmeyer@sbcglobal.net> wrote in message
news:4ckCd.6887$yV1.4264@newssvr14.news.prodigy.com...
> Digital Video Solutions wrote:
> > *Well Wilbert, for someone who "hangs around at the video forums (doom9
> > for example)" it appears that you really don't have a firm grasp on
> > video compression, video resolutions, frame rates or the structure of
> > competitent video analysis whatsoever. When you can stop "hanging around
> > these cool video forums" and grab a set of clients who are actually
> > doing something in the real world of video you can tell everyone how
> > frame resolutions, frame rates, data rates and bitrates have nothing to
> > do with compression.*
>
> It never ceases to amaze me the vigor with which ignorance is
> promulgated online. Having been in professional video since 1968, and
> having spent most of my time in hardware and software design for the
> video industry, it is impressive to see someone like Wilbert make such
> pronouncements that are filled with so much misinformation. Clearly, he
> seems convinced that video was born about the time of the desktop
> computer <g>.
>
> My hat's off to you for setting min straight in a number of areas. I
> generally don't take the time, because (as you may see later) his ilk
> all too often come back with more of the same, and proceed to waste time
> and bandwidth, apparently in the belief that loud screams will overcome
> logic and knowledge.
>
> Bill