Compression

[Adi]

Whats the order listing for compression quality. What order would you put these in 1 being the best.

1. jpeg 2000

2. mpeg 4

3. wavelet

4. m-jpeg

5. jpeg

What do you use as standard?

Is mpeg 4 any good?

Why have some 16 channel dvr s only got 50 fps?

There has been a rew recommendations on here for video switch dvr s but it seems there fps is a bit on the low side, am i wrong?

for any info im trying to sort a couple of dvrs out at the minute and then stick to them, one for domestic one for mid range 8/9 to 16 channel.

[Andy D]

Hi

There is no direct link between compession and image quality

The quality is dependant on a few factors eg recorded resolution,

how well the compression codec has been implemented, and the

video picture its self (some mpeg 4 machines can strugle recording

video with large moving objects)

[breff]

As stated above, compression of video is dependent on what is being recorded, most of the time only the differences between each frame is stored, why store the whole picture when you can say pixels 1-600 as original etc, the more movement/changes the less effective the compression

[Adi]

I am right in thinking spreading 16 channels over 50 fps is **** because on a camera that has only got a small field of veiw with 3 fps is not going to capture a lot.

Also i thought i read a thread on here thet mpeg 4 lost a lot of detail because it was heavily compressed. Have i read and unstood that right or have i got it wrong.

[Andy D]

Also i thought i read a thread on here thet mpeg 4 lost a lot of detail because it was heavily compressed. Have i read and unstood that right or have i got it wrong.

It depends on the machine, some are better then others, Mpeg 4 or any other codec

[Guest Rockford]

Hi

There is no direct link between compession and image quality

The quality is dependant on a few factors eg recorded resolution,

how well the compression codec has been implemented, and the

video picture its self (some mpeg 4 machines can strugle recording

video with large moving objects)

What are you talking about?! Of course there's a connection between quality and codec!! MPEG2 uses virtually no compression and is therefore considered to be the highest quality digital video. MPEG4 uses load of compression which makes files small and streams very well, but quality suffers...

[Guest Rockford]

Whats the order listing for compression quality. What order would you put these in 1 being the best.

1. jpeg 2000

2. mpeg 4

3. wavelet

4. m-jpeg

5. jpeg

Very difficult to say as some are very similar. Note that quality is not the ONLY thing that makes a codec good... Some are naturally better at streaming, some use less CPU time etc. Just in terms of QUALITY, I think:

1. MJPEG

2. JPEG2000

3. JPEG (NOT a video codec)

4. Wavelet

5. MPEG4

[Adi]

for that. I know theres more than one factor in chosing quality on dvr s but atleast ive now got a better understanding of some of it. I thought mpeg 4 was suppose to be quite good but i guess not. Ithought the order i had it in was some where near. It seems a lot of manafactures use mpeg 4 is that so they can store more info on the hard drive?

I think my main concern now is having a decent amount of fps.

[Andy D]

What are you talking about?! Of course there's a connection between quality and codec!! MPEG2 uses virtually no compression and is therefore considered to be the highest quality digital video. MPEG4 uses load of compression which makes files small and streams very well, but quality suffers...

As stated peviously "quality" does not only depend on the codec, if a machine records

352x288 (CIF)resolution using mpeg 2 the "quality" is unlikley to be better than a machine

recording 720X288 (2CIF) or 720x576 (4CIF)using mpeg 4 which have 2 and four times

the resoulution

The quality also depends on the machine and how well it encodes the video.

[Guest Rockford]

As stated peviously "quality" does not only depend on the codec, if a machine records

352x288 (CIF)resolution using mpeg 2 the "quality" is unlikley to be better than a machine

recording 720X288 (2CIF) or 720x576 (4CIF)using mpeg 4 which have 2 and four times

the resoulution

The quality also depends on the machine and how well it encodes the video.

I agree that it does not ONLY depend on the codec, but the codec is the dominant factor in overall video quality. I think your statement is probably not accurate... The MPEG2 record will very likely be better video quality than a much higher res MPEG4 record. MPEG4 is designed for streaming, therefore is heavily compressed whilst MPEG2 is not. I definately agree that the unit's ability to encode will also have a major impact on overall results.

Much more complicated a debate than black and white!!

for that. I know theres more than one factor in chosing quality on dvr s but atleast ive now got a better understanding of some of it. I thought mpeg 4 was suppose to be quite good but i guess not. Ithought the order i had it in was some where near. It seems a lot of manafactures use mpeg 4 is that so they can store more info on the hard drive?

I think my main concern now is having a decent amount of fps.

Ahh, you see; MPEG4 IS quite good! It streams very well, is very small (which as you said, allows lots of video relative to your available storage) and can achieve decent frame rates! the MPEG4 standard allows for a few different levels of quality, the highest of which is "OK"... Enough to convict a London bomber anyways! Major advantage: its ability to dynamically adjust FR and quality for stream playback depending on available bandwidth, major disadvantage: 1. Uses a lot of processor overhead for compression (so use a hardware compressor) 2. Quality isn't too much the best because of massive amounts of compression. Especially noticible when there's LOTS of on-screen activity.