As stated above, why all the compact cam with Video mode so inefficient in file size for video?
Thanks.:thumbsup:
Thanks.:thumbsup:
1st Question! Why can't compact cam give small video size?
- Thread starter lastboltnut
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Poor compression, processor slow, read-write to media slow.
For mainstream video, MiniDV is still pretty much the way to go.
For mainstream video, MiniDV is still pretty much the way to go.
i believe most, if not all compact cams uses motion JPEG instead of MPEG compression. Thats why it has a poor compression ratio.
Slow processor may be....media shouldn't be a problem as I can use SD card to watch very highbandwidth video on my PDA/Laptop...what do you think?
Huh? I tot MPEG is a collection of JPEG liao? Not har....:dunno:
Or may be they are trying to force us to buy another delicated V-Cam, so that they can make more $?
Huh? I tot MPEG is a collection of JPEG liao? Not har....:dunno:
Or may be they are trying to force us to buy another delicated V-Cam, so that they can make more $?
nope.. MPEG and MJPEG is 2 different things. MJPEG is actually JPEGs stacked together to form a video (so the only compression done is when its converted to JPEG) and as for MPEG its does its coding differently.
If you are interested you can read http://www.fileformat.info/format/mpeg/egff.htm for more information. It explains the concepts of MPEG and MJPEG clearly.
If you are interested you can read http://www.fileformat.info/format/mpeg/egff.htm for more information. It explains the concepts of MPEG and MJPEG clearly.
when u watch highbandwidth = READ from SD, but when you are recording its WRITE... so must see if your SD card can support fast write anot, its between 1/2 to 75% of the actual read speed normally.
hmm... mjpeg got sound anot? btw, how big your raw file to make u wanna do DIVX compression...
Generally this happens:
1. The sensor/mic reads the light/sound and translates to electrical signals.
2. The processor first reads the raw signal and record internally as images/sound/data.
3. The compression processor then compresses the raw data into whatever format (MiniDV, DVD, MPEG, DivX, etc.)
4. Then the compressed data is written onto the media (tape, card, harddisc or optical disc).
When you read, the data is retrieved from the media, decompressed by the processor into RAW signal, and sent to the output (monitor, speakers). That is the reverse of the image/sound capture.
The problem is the compressor and the writer. If you have very fast compressor and very fast writer, then you can do a DivX on the go at hi-res and write ontot he fastest media. But not everyone wants compression, especially those who needs lots of post-editing. MiniDV and it brothers are acceptable compression by most indie video, but TV broadcast will reject most miniDV unless no-choice. So, to write less compressed data means faster write needed. To write faster with more compression means that the compression compressor must really fast.
On chips, fast means power-hungry and over-heating.
That's why there is always compromises.
1. The sensor/mic reads the light/sound and translates to electrical signals.
2. The processor first reads the raw signal and record internally as images/sound/data.
3. The compression processor then compresses the raw data into whatever format (MiniDV, DVD, MPEG, DivX, etc.)
4. Then the compressed data is written onto the media (tape, card, harddisc or optical disc).
When you read, the data is retrieved from the media, decompressed by the processor into RAW signal, and sent to the output (monitor, speakers). That is the reverse of the image/sound capture.
The problem is the compressor and the writer. If you have very fast compressor and very fast writer, then you can do a DivX on the go at hi-res and write ontot he fastest media. But not everyone wants compression, especially those who needs lots of post-editing. MiniDV and it brothers are acceptable compression by most indie video, but TV broadcast will reject most miniDV unless no-choice. So, to write less compressed data means faster write needed. To write faster with more compression means that the compression compressor must really fast.
On chips, fast means power-hungry and over-heating.
That's why there is always compromises.
My Canon S3 IS can take video (VGA) with stereo sound for about 8min with 1Gb SD card! So inefficient...so I need to convert to Xvid loh...
big file size is mainly due to compression...the other factor tat make up bigger file size is data collected eg.exposure,color,lighting,resolution...
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