Does the Record Mode affect HDMI output?

[Bruce Dempsey]

Is HDMI affected in any way If record mode is set to either HD-FX, HD-FH, HD-HQ, HD-LP or even one of the SD modes?
In order to extract Higher quality stills from the video, I'll be using an intensity Shuttle to capture Motion Jpeg from the HDMI port of a HDRCX550v and will be using the camera's storage merely as backup and would be happy enough using the HD-LP record mode.
My instinct is that the HDMI will be unaffected by record mode but opinions are welcome

[Arkady Bolotin]

Hi, Bruce:

To answer your question, I’ve downloaded HDR-CX550V blueprints from Frank’s site (Frank's thoughts on HDV - Documentation Index) (thank you Frank, good on you, the excellent site!). So, according to the Overall Block Diagram (page 31), the signal to the HDMI port (as well as to the memory card slot) goes from the AVCHD Codec chip.

As far as I can read such diagrams, it could mean that the recoded mode (HD-FX or else) you selected would apparently affect the HDMI output.

Nevertheless, practice is criterion of the truth. Therefore, the best way is to test this with the camera.

[Ron Evans]

It was my understanding that when recording the output goes directly to the HDMI before encoding and the encoded signal goes on to the memory. The integrated circuit has multiple functions including the driver for the HDMI connector.

In playback the signal comes from the flash memory or hard drive gets decoded and played back out of the HDMI port. I believe it has been this way since HDMI was first installed on the Sony cameras. Maybe someone who uses this regularly can comment as this was the whole point of using Blackmagic cards I believe.

Ron Evans

[Arkady Bolotin]

Yes, Ron, it amazed me too when I was looking at the CX550V blueprints.

Then I downloaded the AX2000 blueprints from the same Frank’s site (sorry, I couldn't find diagrams for the NX5 there).

And what do you think? Everything is by the book. The signal from CMOS Imager passing thru two 512 Mb SDRAM goes to VIDEO OUT AMP (the amplifier, I believe) and afterward directly to HDMI Transmitter which is connected to the HDMI port (see page 32-34).

[Bruce Dempsey]

Thanks Arkady and Ron
The HDMI signal is from mpeg4 and not uncompressed video?
I'll do some tests

[Bruce Dempsey]

The recording mode was altered from Standby to FX to FH and HQ and LP
I'm not seeing any differences within stills taken from the m2ts files
Nor any differences in the grabs via HDMI
Bitrate makes no diference in stills captured from video?

[Arkady Bolotin]

Bruce:

Please observe two pieces I made from your HDMI frame grabs. The first piece has been cut off the LP grab (by the left side of the frame), and the second one – off the FX grab (at the same place).

I might be mistaken but it seems to me that the FX piece has a higher video quality. Look closely: the background is grainier in the LP piece, and in addition, ringing artifacts are more prominent here than in the FX piece.

[Arkady Bolotin]

And here is another pair of the grab pieces...

Yes, I am almost certain now: the LP grab has more compression artifacts than the FX snapshot.

[Bruce Dempsey]

You have a good eye for detail Arkady (literally)
Which group of pictures did you use, The 5 on the right were from the HDMI capture (M-JPEG) and the group of 4 on the left were from the camera's own AVCHD files
Astounding how little perceived difference there is between the highest and lowest bitrate avchd footage
I'm still unclear as to the the question of HDMI ouput. Is it produced pre or post avchd.

Thanks again Arkady

[Ron Evans]

Unless things have changed I still think that recording live from the HDMI will be uncompressed. In other words treating the camcorder as a camera with HDMI output and NOT recording to internal memory at all. I think you need to make sure that you are NOT recording to internal memory when externally recording from the HDMI.

If you record to the camera then play back and record from the HDMI it will be at whatever the AVCHD recording was set to converted to HDMI for output.


Ron Evans

[Bruce Dempsey]

so is the image labeled standby any cleaner than the others.
It might be

[Arkady Bolotin]

It is hard to say unequivocally, but it seems to me like the frame grabbed in standby has the quality even higher than that made in the FX mode.

This may possibly be the evidence backing up Ron’s inference that during standby a pre-compressed signal is output from the HDMI connector.

P.S. I used the pictures captured thru HDMI (five on the right).

[Bruce Dempsey]

All of the stills from the group on the right were from the HDMI ouput which seems to prove that HDMI video mode is indeed affected by the recording mode of the HDR-CX550v- Big surprise to me at least.
Thanks again Ron and Arkady

[Ron Evans]

The HDMI output quality from camera recording will be controlled by what was recorded. This should be no surprise. As I understand the camera logic. If the camera is recording then the HDMI output comes from the recorded file and will thus be dependent on the bit rate chosen. IF the camera is in standby ( NOT recording ) then the HDMI output comes straight from the sensor uncompressed and will be higher quality than any of the recorded files. If you want the highest quality recording using a Blackmagic card then do not let the camera record at the same time, leave it in standby. At least that is my understanding of the camera logic.

Ron Evans