Sdhc cards

A

alarch

Active member
Hello,
Are SDHC cards class10 at 20mbps suficient for 50 or 60p fullhd?
(technically I should not think so ...)
Do we have to go for sandisc extreme pro at 45mps or do someone know of any other afordable cards

And what time do we get for a 16 or a 32giga bite card?
 
I shot 60-frame 1080p to my Class 10 Panasonic Gold SD cards without a problem. I think my 16GB cards could hold around 100 minutes of 1080/24p material.
 
alarch said:
Hello,
Are SDHC cards class10 at 20mbps suficient for 50 or 60p fullhd?
(technically I should not think so ...)
Do we have to go for sandisc extreme pro at 45mps or do someone know of any other afordable cards

And what time do we get for a 16 or a 32giga bite card?
Click to expand...

First off, Class 10 cards are rated to give a MINIMUM sustained transfer rate of 10 MB/s. It is IMPORTANT to note that the capital 'B' signifies "BYTES" not "bits". A lower case 'b' is bits. There are 8 bits in 1 Byte (most codecs are spec'd in bits per seconds rather than Bytes per second, more on this later).

Now most Class 10 cards will deliver a burst of 20 MB/s some as high as 45 MB/s. However don't be fooled by these specs as the reason why you are on this forum thread is likely because you have an NXCAM or a camcorder that records to AVCHD.

Currently the official spec on AVCHD is that it will top out at 24Mb/s (that's bits NOT Bytes). With the FS100 it has extended to 28Mb/s. Therefore in Bytes that's 24/8 = 3MB/s or 28/8 = 3.5MB/s.

Therefore is Class 10 adequate? I think so, since 10MB/s is greater than 3MB/s and 3.5MB/s.

Take note that the newer SDXC cards are available now, and are backwards compatible to SDHC, I recommend SDXC over SDHC for the increased capacity. To ensure compatibility, just make sure your camcorder can read it (i.e. it uses the exFat format, therefore make sure your post-production computer can read it too). SDXC takes SDCards beyond the 32GB capacity limit and takes it all the way to 2TB. By default they all appear to come in Class 10 only. Having said that I'd recommend the Lexar Professional line of SDCards. These offer excellent bang for buck. They currently have 16GB, 32GB, 64GB and 128Gb. I have the 64GB (for $130 on bhphoto) and it works great.
 
ectobuilder said:
Therefore is Class 10 adequate? I think so, since 10MB/s is greater than 3MB/s and 3.5MB/s.
Click to expand...

If you shoot in S&Q Motion mode, it will have significantly higher throughput since the playback is 24Mbit/sec at the FINAL playback speed, which means it's written at 60Mbit/sec.

Regardless, the manual states that class 10 or higher card is needed for HD recording.
 
jetswing said:
If you shoot in S&Q Motion mode, it will have significantly higher throughput since the playback is 24Mbit/sec at the FINAL playback speed, which means it's written at 60Mbit/sec.

Regardless, the manual states that class 10 or higher card is needed for HD recording.
Click to expand...

Still more than enough. Remember, the minimum sustained transfer rate for Class 10 is 10MB/s. That is equivalent to 80Mb/s (Mbps). So it is still higher than the 60Mbps for S&Q.

Just out of curiousity, how is the 60Mb/s calculation done?
 
speedracerlo said:
i got a 32gb sandisk extreme class10 30MB/s for $90
Click to expand...

Pretty much overkill, first off 30MB is = 240 Mbps. No device that uses SDXC/SDHC uses that much bandwidth, just CF or SSD.

Secondly 30MB/s is burst speed I believe not sustained. Oh well 32GB is 32GB I guess.
 
jetswing said:
If you shoot in S&Q Motion mode, it will have significantly higher throughput since the playback is 24Mbit/sec at the FINAL playback speed, which means it's written at 60Mbit/sec.
.
Click to expand...

Thats not true. At 60P data is 28Mb/sec. (28Mbps), yes it means less quality per frame (may be a very litle as for viewable notice, but for sure on data), than recording at 24p.
 
Be carful though, some cards are actually stating max rates. This usually means read rates and not always write speeds. That said, almost any class 10 is more then enough, as they are rated by sustained WRITE speeds.
 
Tony Hernandez said:
Thats not true. At 60P data is 28Mb/sec. (28Mbps), yes it means less quality per frame (may be a very litle as for viewable notice, but for sure on data), than recording at 24p.
Click to expand...

That's not true that that's not true. :p

at 1080p60 data is 28Mbps, yes, but at 60fps S&Q recording to 1080p24 24Mbps, it is 60Mbps.
 
ectobuilder said:
How is this being calculated?
Click to expand...

like this. normal 24p FX is 24Mbps. when you overcrank in S&Q mode, it maintains the 24Mbps, based on 24p. So if you overcrank to 30fps, it records at 30Mbps. 60fps is 60Mbps. That way when the footage is slowed down to 24p, you still have a 24Mbps stream.

So recording 28Mbps 1080/60p is NOT the same as recording 24Mbps 24p, and overcranking to 60. Overcranking is much better quality than native.

Think of it like this. This is not how the data is spread out under normal shooting, but if every frame was equal then....

24P 24Mbps = 1Mb per frame.
60P 28Mbps = .47Mb per frame.

this is why you may use a class 4 SD card for normal shooting, but S&Q requires a class 10 card. It's in the manual.
 
cheezweezl said:
like this. normal 24p FX is 24Mbps. when you overcrank in S&Q mode, it maintains the 24Mbps, based on 24p. So if you overcrank to 30fps, it records at 30Mbps. 60fps is 60Mbps. That way when the footage is slowed down to 24p, you still have a 24Mbps stream.

So recording 28Mbps 1080/60p is NOT the same as recording 24Mbps 24p, and overcranking to 60. Overcranking is much better quality than native.

Think of it like this. This is not how the data is spread out under normal shooting, but if every frame was equal then....

24P 24Mbps = 1Mb per frame.
60P 28Mbps = .47Mb per frame.

this is why you may use a class 4 SD card for normal shooting, but S&Q requires a class 10 card. It's in the manual.
Click to expand...

How did you conclude that in S&Q mode, there is a 1-to-1 relationship between frame rates and data rate (i.e. 1fps = 1megabit)?
 
well there isn't a 1:1 ratio really. it's actually variable bit rate and is content dependent. but my point is that is maintains it's relative bit rate when overcranking. so that means 24Mbps at 24fps equates to 60Mbps at 60fps in S&Q mode. this is an old issue that came up when the ex1 was first released. it was a debate between overcranking to 60fps in 720p/24 mode, or just shooting 720p/60 and slowing in post. same principle applies here...
 
You can test this, record for 10 seconds in both modes. Check the file size in each mode, divide that by 10, that's how much data is recorded on the card each second.
 
cheezweezl said:
like this. normal 24p FX is 24Mbps. when you overcrank in S&Q mode, it maintains the 24Mbps, based on 24p. So if you overcrank to 30fps, it records at 30Mbps. 60fps is 60Mbps. That way when the footage is slowed down to 24p, you still have a 24Mbps stream.

So recording 28Mbps 1080/60p is NOT the same as recording 24Mbps 24p, and overcranking to 60. Overcranking is much better quality than native.

Think of it like this. This is not how the data is spread out under normal shooting, but if every frame was equal then....

24P 24Mbps = 1Mb per frame.
60P 28Mbps = .47Mb per frame.

this is why you may use a class 4 SD card for normal shooting, but S&Q requires a class 10 card. It's in the manual.
Click to expand...


AVCHD is max at 24mbps, sony implements up to 28mbps for 60p.
This means 28 divided by 60 frames, this means that to have the same quality as for 24P it need to be rated at 60mbps and not 28mbps like sony mentions on its specs, this means -over my tech. point of view- that recoding at 60P have 0.466Mb per frame like you write.

So and as notice:
24P 24Mbps = 1Mb per frame.
60P 28Mbps = 0.47Mb per frame.

So at 60P the quality per frame is inferior.

I hope to be wrong, i wish, but maths
 
Tony Hernandez said:
I hope to be wrong, i wish, but maths
Click to expand...

congrats, you get your wish. AVCHD may max out at 28Mbps but that would be in it's playback format. The FS100 records 60fps S&Q at 60Mbps with the intention of a file that plays back at 24Mbps. That's why you need class 10 cards to do it.

I just did the test so I could reassure myself and others. I recorded 10 seconds (roughly, by my iphone's stopwatch) of 1080p/60 28Mbps, and then 1080p/24 24Mbps overcranked to 60 frames.

the two files which contain the same number of frames (+/- 10% for human error), are completely different when it comes to file size. the 1080p/60 file is 35.9MB. The 1080p24 file is 76MB.

So, lets translate that file size to bit rate. 76MB x 8 = 608Mb. Then, 608Mb ÷ 10sec = 60.8Mbps. Now I can't claim to have recorded exactly 10 seconds, But I can say with confidence that I was off by less than one second. So this all adds up to 60frame overcrank at 24p FX records at 60Mbps.

And just in case you were wondering. If I do the same math on the 1080p/60 file, it comes out to 28.72Mbps. Exactly what it should be.


harrisoncj said:
It shoots 1080 60p on my class 6 Sandisk. I didn't think it would but I tried it out today.
Click to expand...

1080/60P or 1080/24P overcranked to 60? If it's 24p, then that is good news for all of us. class 6 cards are dirt cheap!!! If it was 1080/60P, you can actually do that with a class 4 card, according to sony...
 
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