BMPCC- A few questions on dropped frames, record times and Codecs

[Stephen Henderson]

Hi DvInfo users,

I recently bought the BMPCC, and have been enjoying it.

A few questions I havn't been able to find answers to:

-Is there a to check to see if a file has dropped frames after the fact? (Apart from just watching it?)

-Does anyone have experience recording for long periods of time at Prores Lt or Proxy?

-Does anyone who how Prores Proxy would compare to the H264 Codec from the older Canon DLSRs (Like the t3i)?

Thanks!

-Stephen

[Ricky Sharp]

Originally Posted by Stephen Henderson

Does anyone who how Prores Proxy would compare to the H264 Codec from the older Canon DLSRs (Like the t3i)?

According to the ProRes whitepaper, Proxy would have a bitrate of 36 Mbps for 1080p at 24 fps. If I did the math correctly, that would be about a 3.4:1 compression ratio. Assuming the T3i uses a bitrate of 24 Mbps for the same footage, that would be about a 3:1 compression ratio. So compression fairly close.

But the Proxy footage would be 10-bit 4:2:2 (vs the 8-bit 4:2:0 from the T3i). So while it could have more compression artifacts, the color would be much better.

Disclaimer: I don't own either camera; this is just some rough calculations on paper.

[Stephen de Vere]

I think it might be a mistake to directly compare the two codecs like that.

You generally need at least 2x the data rate with I-frame codecs like ProRes (all flavours) to equal long-gop type compression that I think AVCHD uses.