Sony XAVC-S 50mbs (Consumer) Micro SDXC recording time specs

[demoboy]

I am going to buy 3 new Sony HDR-CX405 cams. They'll mainly be used for rough sketch productions as I have team for reality show creation. We need a full day of shooting so I assume 128gb cards can cover 10 hours? It is my understanding that I can only record one stream of XAVC-S to a card and the second stream as a "proxy" quality backup which wouldnt eat as much. what are recording time specs anyone? thnx

 

[AtticusLake]

If it's 50 Mb/s, well... that's 50 Mbits of data going onto your card per second, or 50 / 8 = 6.25 MB (megabytes) per second; or 22 GBytes per hour. So around 200 GB for 10 hours.

It's not quite that simple; the actual recording rate will be slightly variable, due to varying compressibility of the signal, and you may have to allow for the audio track if the 50 mb/s just applies to the video. But basically, that should give you a ballpark figure.

As for proxies, the B&H page for that camera says "... dual recording, which lets you simultaneously capture both high-quality AVCHD and web-optimized MP4 files". Sounds like you can only dual record in AVCHD, so the primary will be 28 Mb/s in that case. Personally, I would shoot XAVC.

Oh, and bear in mind that a "128GB" card doesn't actually have 128 GB of usable space.

 

[demoboy]

thank you sir. This is what the UK Sony site states with the picture attached below. Btw, do you think Class 10 SDXC at a write speed of 10mbs (usual average) is ok for XAVC-S? Or should I not risk it and go with UHS-I (U3) ? I see, so at 3mbs at MP4 (from sony site) I should get about 1.4gb / hour. Thanks for the help.

For the footnote it states:

1. 2Not available in AVCHD PS mode and XAVC S HD 60p mode.

 

[AtticusLake]

Ah, OK, I guess it can proxy with XAVC! Cool! As for the data rate, sounds like you've got it worked out. Based on what I've seen on other Sonys, their idea of "Web-ready MP4" is pretty low-quality, and hence low-bitrate.

As to the cards: class 10 is supposedly "10 MB/s [80 Mbits per second] as a minimum non-fragmented sequential write speed". So on a fragmented card it could get slower.

(BTW Mb/s -- lower-case "b" -- is megabits per second; MB/s -- upper-case "B" -- is megaBYTES per second, which is 8 times as much.)

OTOH, UHS class 1 is "minimum read/write performance of at least 10 MB/s [80 Mbits per second]". I think the UHS classes are a little more stringent about the minimum that a card must handle at all times, so even though the number s the same, it may be a little more reliable.

It's all a little vague, because it depends on how fragmented the card is, and on how its internal electronics work. For example some higher-quality cards have more internal RAM buffering to smooth over this kind of thing. BTW flash memory is a little crazy -- it can be fragmented even when the card is empty.

So I guess class 10 should be OK; you've got 30 Mb/s of headroom to get over any glitches. U1 might offer a little more security in that regard, though. I would say check the camera manual, but I can't seem to find it -- it might not be out yet.