Possible Multiple DM365 Sharing The Same Hard Disk Drive?

You could use One DM365 as a USB Host and other as USB Device along with a USB HDD.  The slave DM365 and USB HDD can be connected to the Host DM365 using a 2 port Hub.  In this way you can pass on the streams from the slave DM365 to Host DM365 to be stored on the HDD.

regards

swami

Swami probably has the most optimal method for two local DM365 devices, one other way I could see doing this would be to have both DM365 devices connected to a network with network addressable storage (NAS) holding the HDD, this would have more hardware to setup but would be more scaleable and allows for more flexibility in location of each component.

DM365          DM365
         \              /
           Ethernet  
            Switch  
                |      
        NAS / HDD

A similar solution closer to what Swami suggested would be to have one device host the HDD over USB with both DM365s connected to the same network, and have the DM365 with the HDD act as a NAS so that the other DM365 can still write to it, so you have a master slave setup but use Ethernet instead of a USB connection between DM365s.

DM365 ---- Ethernet ---- DM365 ---- USB ---- HDD

Hi,

Since my project currently is DVR application, both DM365 will be located locally and Swami idea is more suitable.

Overall is the architecture achievable or is there any bottleneck that might cause this idea to fail?

I would like to know is the USB bandwidth big enough for cater for these data transfer (

video footage from DM365 host -> HDD

video footage from DM365 slave - > DM365 host -> HDD

video footage from HDD -> DM365 host

video footage from HDD -> DM365 host -> DM365 slave)

Besides USB bandwidth, is the DM365 host able to handle in this snenario? What would be the estimated CPU utilization both DM365 master and DM365 slave?

Can you provide the expected throughput numbers for the path's that you had mentioned in your last post.  Can you also comment whether all the above paths will be present at the same time, if not which of these paths will be occur at the given point in time.  Accordingly I can comment on the DM365 USB capcabality and any concerns that I would see on your use case scenario.

regards

swami

Hi Swami,

Maybe is better if I let you know what I should accomplish with the final product. Please refer below for draft specification of my product

1. support 4 CH of D1 video signal encode into H.264 and stored into hard disk

2. Able to take in video signal either from IP camera or normal CVBS signal camera

3. Video streaming 4CH (each with CIF resolution) signal out from the board

4. Support at least 2 client on video streaming request

All the the above shall happen simultaneously. Reference design of DM365 stated it can only support up to 2 - D1 simultaneously, that where my question of 2 DM365 comes in (in order to support 4 CH of D1 video).

Thank you very much.

cheng

hi,

I am involved in the DM365 DVR reference design so I can help a bit over here.

- DM365 has max capability of of upto 2Ch D1 @ 30fps each
- So to do 4CH D1 @ 30fps each, you will need two DM365
- The HDD can be connected via USB interface to main/host DM365
- The 2nd DM365 can act as slave and send the compressed bitstream to host DM365 via USB
- The host DM365 then streams the 4Ch data over network and/or stores to HDD

Possible bottlenecks (assuming worst 1MB/s data rate per D1 CH, 128KB/s data rate for CIF channel)

- USB throughput in system for Host DM365
  - Need 1MB/s x 2 USB read and 1MB/s x 4 USB write speed atleast
  - Swami can confirm if this is possible (I think yes this is possible)
- Network speed
  - Need 128KB/s x 4 x 2 (clients) Stream out speed
  - This should be easily possible I think
- ARM CPU load would be a concern. Right now for 2CH D1 we see below CPU loading

Some questions from my side,
- How do you plan to get 2Ch D1 into the DM365. We use TVP5158 in DVR reference design ?
- Do you need any de-interlacing ? We do de-interlacing on display via external chip in DVR reference design.
- Do you need local display for all 4 channels ? DVR reference design supports local display with GUI and USB mouse

regards
Kedar

Cheng,

Based on Kedar's response I assume that the max throughput requirement per channel would be 1MBps.  Based on this I can estimate the following.

video footage from DM365 host -> HDD   (2 x 1)  : 2MBps

video footage from DM365 slave - > DM365 host -> HDD  (2 x 2)  :  4 MBps

video footage from HDD -> DM365 host     (2 x 2) : 4 MBps

video footage from HDD -> DM365 host -> DM365 slave  (2 x 1) : 2 MBps

A total of 6MBps Rx + 6 MBps Tx.

DM365 USB can very well handle this throughput.

regards

swami

Hi Swami,

Thanks for your calculations. I appreciated your help.

Hi Kedar Chitnis,

Looking at your CPU calculation (Capture+Resize+Display+2Ch D1 H264 Encode + Storage + Network Stream = 225Mhz (75% CPU loading)) suggest me that this is not the right chip for my product.

Thus, I am now considering DM6467, I believe DM6467 processing power shall be able to cope with my requirement, am I right?

However, if using DM6467, my concern is it possible to port features (video streaming, recording, playback, ip camera support, video timestamp) from DM365 DVR reference design in DM6467? Would it be to complicated to do that?

As for your question:

How do you plan to get 2Ch D1 into the DM365. We use TVP5158 in DVR reference design ?

I am planning to use TVP5158 as well.

Do you need any de-interlacing ? We do de-interlacing on display via external chip in DVR reference design.

For display side will only require CVBS signal, thus i believe de-interlacing is not require.

Do you need local display for all 4 channels ? DVR reference design supports local display with GUI and USB mouse

At any one time 1 channel will be good enough, maybe switchable between the 4 channels.

DM6467 should be no problem,

video streaming, recording, playback, ip camera support, video timestamp should be portable from DM365 to DM6467. This will take some effort but will not be too tough I feel.