K7 video and Memory cards, or how to fix a 720P problem

osv · 09-20-2009, 08:58 AM

maybe i need to re-phrase it, so that people will understand.

720p is *more* than 6MBps, so if the card won't work with 720p, try it with any other recording mode.

juice · 09-20-2009, 09:53 AM

Just for reference, I have an 8GB Sandisk Extreme III card bought ~1 year ago. My K7 shows available time of 19 minutes and when I start recording it then adjusts to show over 9 minutes remaining. Therefore I suspect Extreme III cards should be able to shoot at least 9 minutes continuously (overheating sensor notwithstanding).

In practice I rarely shoot more than 3-4 minutes at a time. Never have any heat problems.

jogiba · 09-20-2009, 11:55 AM

My K-7 with 16GB Sandisk Extreme III 30mb/sec SDHC card shows 9min 35sec when I start recording in 720p *** mode and 7min 23sec in 1024p *** mode that is about the same listed in the K-7 manual for the 4GB limit (FAT32).

osv · 09-20-2009, 01:04 PM

you need to run actual tests.

get your stopwatch out, record 720p for exactly one minute, then record exactly one minute of "1024p" video.

compare the file sizes, using your computer.

jogiba · 09-20-2009, 01:34 PM

The data rates are a little higher in 720p *** than they are in 1024p *** when I checked my videos in Quicktime.

osv · 09-20-2009, 03:06 PM

Originally posted by jogiba

The data rates are a little higher in 720p *** than they are in 1024p *** when I checked my videos in Quicktime.

good, that would back up what i posted on the previous page, about 720p bitrate being higher than the class 6 minimum specification.

pentax mis-represented the 720p bitrate.

so the problems that people are having with 720p recording may not be the fault of the card, rather, it could be because pentax gave us a bitrate that is higher than the minimum class 6 specification.

jogiba · 09-20-2009, 03:24 PM

I don't have any problems doing 720p *** mode HD videos with my K-7 using a 16GB Sandisk Extreme III 30mb/sec SDHC card. I don't see the point of trying to see what is the cheapest SDHC card that will do 720p *** HD video.

osv · 09-20-2009, 04:38 PM

16 gigs is nothing when it comes to shooting video, especially with this mjpeg codec that pentax is using.

jogiba · 09-20-2009, 04:58 PM

Originally posted by osv

16 gigs is nothing when it comes to shooting video, especially with this mjpeg codec that pentax is using.

I don't have a storage problem since I have a bunch of 8GB Extreme III SDHC cards and I download the videos to my laptop. When the 32GB Class 10 SDHC cards drop in price I will pick one up but I am in no rush to get one until then.

falconeye · 09-20-2009, 06:27 PM

K-7 video can exceed 6MB/s and to be on the safe side, there is the forthcoming class 10 spec or the 20/30 MB/s Sandisk cards.

With a card fast enough and at least 4GB free space left, the recording times are exactly as in the manual listed for 4GB. Actual file sizes will be smaller.

Originally posted by osv

pentax mis-represented the 720p bitrate.

Pentax represented the maximum bitrate. It is variable depending on the content. Noise (high ISO) will lead to higher bitrates.

I suspect that the MJPEG compression parameters are slightly more aggressive in 1024p mode and can lead to smaller file sizes than 720p. But in high ISO situations and busy content this may turn out to be different.

osv · 09-22-2009, 09:00 AM

Originally posted by falconeye

Pentax represented the maximum bitrate. It is variable depending on the content. Noise (high ISO) will lead to higher bitrates.

all available data proves that 720p mode records at over 6MBs.

according to that data, there is no situation where 720p mode records at 6MBs or less.

since you feel differently, perhaps you could record some 720p footage for us that is less than 6MBs, and post it up where we can check it out.

by creating a recording mode that exceeds the class 6 sdhc card spec, pentax has misrepresented the capability of 720p mode to record to those cards.

jogiba · 09-22-2009, 10:00 AM

Originally posted by osv

all available data proves that 720p mode records at over 6MBs.

according to that data, there is no situation where 720p mode records at 6MBs or less.

since you feel differently, perhaps you could record some 720p footage for us that is less than 6MBs, and post it up where we can check it out.

by creating a recording mode that exceeds the class 6 sdhc card spec, pentax has misrepresented the capability of 720p mode to record to those cards.

The 30mb/sec Extreme III SDHC cards were stamped Class 6 because there was no Class 10 rating at the time they came out so Pentax is not wrong. It's the clueless people looking to buy the cheapest Class 6 SDHC cards that have a problem.

falconeye · 09-22-2009, 01:14 PM

Originally posted by osv

since you feel differently

Read again

osv · 09-22-2009, 06:31 PM

Originally posted by jogiba

It's the clueless people looking to buy the cheapest Class 6 SDHC cards that have a problem.

i hear what you are saying, but it's not their fault that pentax mis-represented the write speed of the camera.

how many canon users are having these sdhc problems with their 5dII or 7d?

falconeye · 09-23-2009, 02:51 AM

Originally posted by osv

pentax mis-represented the write speed of the camera.

Please stop making false statements. This is confusing.

E.g., for 720p 3star quality, the Pentax manual p.310 states an approximate recording time of 9:26 for 4GB storage which actually turns out to be an ensured recording time with file size to be 4GB or less.

This translates to a recording bandwidth of 57.9 MBit/s or less, i.e. 7.24 MByte/s or less, exceeding the Class 6 minimum requirements (i.e., while some Class 6 cards would work ok, others won't). Class 6 Sandisk Extreme III cards work ok.

For 1024p 3 star quality, the manual spec translates even to 74.0 MBit/s or less, i.e. 9.25 MByte/s or less. So, where on earth do you read that any Class 6 card would suffice? As it is the best available SD card Class, just some of them will do and Pentax doesn't say otherwise.

Typical recording bandwidth for 720p 3star quality are 44 MBit/s or 5.5 MByte/s and therefore, in good light more cards may work with 720p 3 star quality.

BTW.
The 720p 2 star quality records at 41.0 MBit/s or less, i.e. 5.13 MByte/s or less. So, any properly tagged Class 6 card suffices to record 720p 2 star quality.

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09-20-2009, 08:58 AM	#16
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	maybe i need to re-phrase it, so that people will understand. 720p is more than 6MBps, so if the card won't work with 720p, try it with any other recording mode.

09-20-2009, 09:53 AM	#17
juice Forum Member Join Date: Sep 2007 Location: Gold Coast, Australia Posts: 64	Just for reference, I have an 8GB Sandisk Extreme III card bought ~1 year ago. My K7 shows available time of 19 minutes and when I start recording it then adjusts to show over 9 minutes remaining. Therefore I suspect Extreme III cards should be able to shoot at least 9 minutes continuously (overheating sensor notwithstanding). In practice I rarely shoot more than 3-4 minutes at a time. Never have any heat problems.

09-20-2009, 11:55 AM	#18
jogiba Banned Join Date: Sep 2006 Location: Millstone,NJ Posts: 6,491	My K-7 with 16GB Sandisk Extreme III 30mb/sec SDHC card shows 9min 35sec when I start recording in 720p * mode and 7min 23sec in 1024p * mode that is about the same listed in the K-7 manual for the 4GB limit (FAT32).

09-20-2009, 01:04 PM	#19
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	you need to run actual tests. get your stopwatch out, record 720p for exactly one minute, then record exactly one minute of "1024p" video. compare the file sizes, using your computer.

09-20-2009, 01:34 PM	#20
jogiba Banned Join Date: Sep 2006 Location: Millstone,NJ Posts: 6,491	The data rates are a little higher in 720p * than they are in 1024p * when I checked my videos in Quicktime.

09-20-2009, 03:06 PM	#21
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	Originally posted by jogiba The data rates are a little higher in 720p * than they are in 1024p * when I checked my videos in Quicktime. good, that would back up what i posted on the previous page, about 720p bitrate being higher than the class 6 minimum specification. pentax mis-represented the 720p bitrate. so the problems that people are having with 720p recording may not be the fault of the card, rather, it could be because pentax gave us a bitrate that is higher than the minimum class 6 specification.

09-20-2009, 03:24 PM	#22
jogiba Banned Join Date: Sep 2006 Location: Millstone,NJ Posts: 6,491	I don't have any problems doing 720p * mode HD videos with my K-7 using a 16GB Sandisk Extreme III 30mb/sec SDHC card. I don't see the point of trying to see what is the cheapest SDHC card that will do 720p * HD video.

09-20-2009, 04:38 PM	#23
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	16 gigs is nothing when it comes to shooting video, especially with this mjpeg codec that pentax is using.

09-20-2009, 04:58 PM	#24
jogiba Banned Join Date: Sep 2006 Location: Millstone,NJ Posts: 6,491	Originally posted by osv 16 gigs is nothing when it comes to shooting video, especially with this mjpeg codec that pentax is using. I don't have a storage problem since I have a bunch of 8GB Extreme III SDHC cards and I download the videos to my laptop. When the 32GB Class 10 SDHC cards drop in price I will pick one up but I am in no rush to get one until then.

09-20-2009, 06:27 PM	#25
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	K-7 video can exceed 6MB/s and to be on the safe side, there is the forthcoming class 10 spec or the 20/30 MB/s Sandisk cards. With a card fast enough and at least 4GB free space left, the recording times are exactly as in the manual listed for 4GB. Actual file sizes will be smaller. Originally posted by osv pentax mis-represented the 720p bitrate. Pentax represented the maximum bitrate. It is variable depending on the content. Noise (high ISO) will lead to higher bitrates. I suspect that the MJPEG compression parameters are slightly more aggressive in 1024p mode and can lead to smaller file sizes than 720p. But in high ISO situations and busy content this may turn out to be different.

09-22-2009, 09:00 AM	#26
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	Originally posted by falconeye Pentax represented the maximum bitrate. It is variable depending on the content. Noise (high ISO) will lead to higher bitrates. all available data proves that 720p mode records at over 6MBs. according to that data, there is no situation where 720p mode records at 6MBs or less. since you feel differently, perhaps you could record some 720p footage for us that is less than 6MBs, and post it up where we can check it out. by creating a recording mode that exceeds the class 6 sdhc card spec, pentax has misrepresented the capability of 720p mode to record to those cards.

09-22-2009, 10:00 AM	#27
jogiba Banned Join Date: Sep 2006 Location: Millstone,NJ Posts: 6,491	Originally posted by osv all available data proves that 720p mode records at over 6MBs. according to that data, there is no situation where 720p mode records at 6MBs or less. since you feel differently, perhaps you could record some 720p footage for us that is less than 6MBs, and post it up where we can check it out. by creating a recording mode that exceeds the class 6 sdhc card spec, pentax has misrepresented the capability of 720p mode to record to those cards. The 30mb/sec Extreme III SDHC cards were stamped Class 6 because there was no Class 10 rating at the time they came out so Pentax is not wrong. It's the clueless people looking to buy the cheapest Class 6 SDHC cards that have a problem.

09-22-2009, 01:14 PM	#28
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by osv since you feel differently Read again

09-22-2009, 06:31 PM	#29
osv Veteran Member Join Date: Mar 2007 Location: So Cal Photos: Gallery Posts: 2,080	Originally posted by jogiba It's the clueless people looking to buy the cheapest Class 6 SDHC cards that have a problem. i hear what you are saying, but it's not their fault that pentax mis-represented the write speed of the camera. how many canon users are having these sdhc problems with their 5dII or 7d?

09-23-2009, 02:51 AM	#30
falconeye Veteran Member Join Date: Jan 2008 Location: Munich, Alps, Germany Photos: Gallery Posts: 6,871	Originally posted by osv pentax mis-represented the write speed of the camera. Please stop making false statements. This is confusing. E.g., for 720p 3star quality, the Pentax manual p.310 states an approximate recording time of 9:26 for 4GB storage which actually turns out to be an ensured recording time with file size to be 4GB or less. This translates to a recording bandwidth of 57.9 MBit/s or less, i.e. 7.24 MByte/s or less, exceeding the Class 6 minimum requirements (i.e., while some Class 6 cards would work ok, others won't). Class 6 Sandisk Extreme III cards work ok. For 1024p 3 star quality, the manual spec translates even to 74.0 MBit/s or less, i.e. 9.25 MByte/s or less. So, where on earth do you read that *any* Class 6 card would suffice? As it is the best available SD card Class, just *some of them* will do and Pentax doesn't say otherwise. *Typical* recording bandwidth for 720p 3star quality are 44 MBit/s or 5.5 MByte/s and therefore, in good light more cards may work with 720p 3 star quality. BTW. The 720p 2 star quality records at 41.0 MBit/s or less, i.e. 5.13 MByte/s or less. So, *any* properly tagged Class 6 card suffices to record 720p 2 star quality.