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J
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      11-23-2011, 12:43 AM

I'm not too clued up on video issues, but I always thought AVI meant '640 x
480'. The thing is, my 'old' Sony P93 digicam produces a video which is 640
x 480 and a 3 minute video would be app., 60MB in size. But...'I have a
newer Canon SX130 IS which produces 720 HD video and also '640 x 480' video,
but the later takes up 300MB for a 3 minute video. Why does the Canon's 640
x 480 video take up SIX times the room of the Sony 640 x 480 video?

J



 
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Laszlo Lebrun
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      11-23-2011, 07:45 AM
On 23.11.11 01:43, J wrote:
> I'm not too clued up on video issues, but I always thought AVI meant '640 x
> 480'. The thing is, my 'old' Sony P93 digicam produces a video which is 640
> x 480 and a 3 minute video would be app., 60MB in size. But...'I have a
> newer Canon SX130 IS which produces 720 HD video and also '640 x 480' video,
> but the later takes up 300MB for a 3 minute video. Why does the Canon's 640
> x 480 video take up SIX times the room of the Sony 640 x 480 video?
>
> J
>

it might be the different compression, very probably the SX130 takes a
true 480P video whereas the p93 takes only interlaced.
The picture might also be much crisper, with a lot more details, harder
to compress.


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J
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      11-23-2011, 11:45 AM

"Laszlo Lebrun" <(E-Mail Removed)> wrote in message
news:jai8at$32a$(E-Mail Removed)...
> On 23.11.11 01:43, J wrote:
>> I'm not too clued up on video issues, but I always thought AVI meant '640
>> x
>> 480'. The thing is, my 'old' Sony P93 digicam produces a video which is
>> 640
>> x 480 and a 3 minute video would be app., 60MB in size. But...'I have a
>> newer Canon SX130 IS which produces 720 HD video and also '640 x 480'
>> video,
>> but the later takes up 300MB for a 3 minute video. Why does the Canon's
>> 640
>> x 480 video take up SIX times the room of the Sony 640 x 480 video?
>>
>> J
>>

> it might be the different compression, very probably the SX130 takes a
> true 480P video whereas the p93 takes only interlaced.
> The picture might also be much crisper, with a lot more details, harder to
> compress.
>


Yes, it does look like the SX130 is producing a much more detailed video
than the Sony does. How different might the audio be in these cameras in
these cameras I wonder? The SX130 sounds more natural than the Sony and has
better bass, but I don't know how different they are technically.

J



 
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OG
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      11-23-2011, 11:06 PM
On 23/11/2011 00:43, J wrote:
> I'm not too clued up on video issues, but I always thought AVI meant '640 x
> 480'. The thing is, my 'old' Sony P93 digicam produces a video which is 640
> x 480 and a 3 minute video would be app., 60MB in size. But...'I have a
> newer Canon SX130 IS which produces 720 HD video and also '640 x 480' video,
> but the later takes up 300MB for a 3 minute video. Why does the Canon's 640
> x 480 video take up SIX times the room of the Sony 640 x 480 video?
>
> J


VGA means 640 x 480

AVI is a file format (or altenatively a container format).

 
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Joel
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      11-24-2011, 12:31 AM
"J" <(E-Mail Removed)> wrote:

> I'm not too clued up on video issues, but I always thought AVI meant '640 x
> 480'. The thing is, my 'old' Sony P93 digicam produces a video which is 640
> x 480 and a 3 minute video would be app., 60MB in size. But...'I have a
> newer Canon SX130 IS which produces 720 HD video and also '640 x 480' video,
> but the later takes up 300MB for a 3 minute video. Why does the Canon's 640
> x 480 video take up SIX times the room of the Sony 640 x 480 video?
>
> J


You can always search Google for more clue. The 640x480 is the 4:3 ratio
aspect of MPEG-2

Just like image, the 640x480 video has nothing to do with the SIZE, cuz
it's just part of the whole format. Or it's *missing* some VALUE to be a
complete value

IMAGE has W x H x P (some prog calls Resolution)

VIDEO has W x H x Frame x BitRate

Just like IMAGE the value of "P" can change the SIZE, with VIDEO the
BitRate can also change the SIZE of video

Example, 640x480 will fit the old analog TV screen, the BitRate is the
QUALITY of the video.

And it doesn't always mean the higher BitRate the higher quality (only to
the MAX of the original), but higher BitRate will create larger SIZE.

Example if you have a 640x480x10000, and you tell the converter or author
to change it to 640x480x8000 then the size will be around 8X larger. And
the quality is still 1X or less comparing to the original.
 
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Gordon Freeman
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      11-24-2011, 12:52 AM
"J" <(E-Mail Removed)> wrote:
>
> I'm not too clued up on video issues, but I always thought AVI meant
> '640 x 480'. The thing is, my 'old' Sony P93 digicam produces a video
> which is 640 x 480 and a 3 minute video would be app., 60MB in size.
> But...'I have a newer Canon SX130 IS which produces 720 HD video and
> also '640 x 480' video, but the later takes up 300MB for a 3 minute
> video. Why does the Canon's 640 x 480 video take up SIX times the room
> of the Sony 640 x 480 video?


AVI is a container format, it can be any resolution and the video can be
compressed with one of many codecs. Another common picture size is
320x240.

The most likely reason for the Canon using 300MB for a 3 minute video is
that it will be using MJPEG compression, which is effectively a stream
of jpegs (25 or 30 a second) wrapped in an AVI container. This is very
easy for a stills camera to produce without special hardware being
required, but is also very inefficient from a compression POV. The Sony
was probably using an MPEG4 format in which only the frame-to-frame
differences are stored which would certainly achieve the 5-fold space
saving you mention.

There is an advantage to the inefficient MJPEG compression method
though: every frame is a keyframe (whole picture) so it is easy to edit
the video without re-encoding, whereas with MPEG4 there is typcially
only a keyframe once every 10 seconds or so which means edits either
have to be cruder or else you have to recompress some or all of the
video which loses quality and takes many times longer. So if space is
no object, MJPEG is more flexible, but the penalty is that you only
get about 10 minutes of video per gigabyte, whereas MPEG4 may give you
an hour or more per gigabyte (depending on what quality and resolution
you use).

 
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Pete A
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      11-24-2011, 10:13 AM
On 2011-11-24 00:52:28 +0000, Gordon Freeman said:

> "J" <(E-Mail Removed)> wrote:
>>
>> I'm not too clued up on video issues, but I always thought AVI meant
>> '640 x 480'. The thing is, my 'old' Sony P93 digicam produces a video
>> which is 640 x 480 and a 3 minute video would be app., 60MB in size.
>> But...'I have a newer Canon SX130 IS which produces 720 HD video and
>> also '640 x 480' video, but the later takes up 300MB for a 3 minute
>> video. Why does the Canon's 640 x 480 video take up SIX times the room
>> of the Sony 640 x 480 video?

>
> AVI is a container format, it can be any resolution and the video can be
> compressed with one of many codecs. Another common picture size is
> 320x240.
>
> The most likely reason for the Canon using 300MB for a 3 minute video is
> that it will be using MJPEG compression, which is effectively a stream
> of jpegs (25 or 30 a second) wrapped in an AVI container. This is very
> easy for a stills camera to produce without special hardware being
> required, but is also very inefficient from a compression POV. The Sony
> was probably using an MPEG4 format in which only the frame-to-frame
> differences are stored which would certainly achieve the 5-fold space
> saving you mention.
>
> There is an advantage to the inefficient MJPEG compression method
> though: every frame is a keyframe (whole picture) so it is easy to edit
> the video without re-encoding, whereas with MPEG4 there is typcially
> only a keyframe once every 10 seconds or so which means edits either
> have to be cruder or else you have to recompress some or all of the
> video which loses quality and takes many times longer. So if space is
> no object, MJPEG is more flexible, but the penalty is that you only
> get about 10 minutes of video per gigabyte, whereas MPEG4 may give you
> an hour or more per gigabyte (depending on what quality and resolution
> you use).


That makes a lot of sense. However, the Canon spec for the SX130 IS
says the file type for movies is MOV [H.264 + Linear PCM (stereo)],
which is MPEG-4 AVC.

For images with a lot of movement, H.264 gives little compression
advantage of M-JPEG. H.264 reduces file size when inter-frame changes
are small.

 
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