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STM32F407 problem using DCMI with embedded sync (ITU656)

rg256
Associate
Posted on October 26, 2012 at 23:50

I trying to use DCMI Interface connected to external video decoder IC ''TVP5150''. DCMI Interface is configured in Snapshot mode (single frame) and to use embedded data synchronization codes (ITU656) in ''Mode 1'' as described in STM32F4 Reference manual ''Doc ID 018909 Rev 2'' on page 280.

Video decoder IC ''TVP5150'' is working too in mode ITU656 and generating correct embedded sync codes in video data stream  (SAV / EAV blanking, SAV / EAV active video).

But STM32F4 is not able extract sycronisation (hsycn, vsync) from ITU656 in a correct way. STM32 is always generating ''IT_ERR'' (Indicates the detection of an error in the embedded synchronization frame detection) and not grabbing video data.

After research i found out that the reason for that behavior is the order of sync code ''SAV active video'' and ''EAV active video'' in data stream. STM32F4 is expecting in ''Mode 1'' that after sync code FEC (frame end delimiter) is following a LSC (line start limiter = SAV) as decribed in ''Doc ID 018909 Rev 2'' page 293.

STM32F4 is expecting something like that:

... [FEC]...

line n+0: [SAV] [active video data] [EAV] [horizontal blanking]

line n+1: [SAV] [active video data] [EAV] [horizontal blanking]

line n+2: [SAV] [active video data] [EAV] [horizontal blanking]

...

But video decoder IC is generating sync codes in opposite way (line starts with EAV and not SAV):

... [FEC]...

line n+0: [EAV] horizontal blanking] [SAV] [active video data]

line n+1: [EAV] horizontal blanking] [SAV] [active video data]

line n+2: [EAV] horizontal blanking] [SAV] [active video data]

...

Anybody have an idea how to configure STM32F4 register ''DCMI_ESCR'' and DCMI_ESUR'' (or maybe other register) that it can be used for ITU656 ?

#translation
5 REPLIES 5
vaidasmikalajunas
Associate II
Posted on April 14, 2014 at 21:15

Hello, 

did You find the solution for this problem?

Amel NASRI
ST Employee
Posted on April 16, 2014 at 10:35

Hi Vaidas,

It should be better to describe clearly your issue so that community members can help you.

Please create a new discussion for this purpose.

-Mayla-

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Posted on April 16, 2014 at 16:57

Assume the salient keywords are TVP5150, ITU656 and DCMI

Does ST have any app notes related to using DCMI with assorted video sources and decoders?

Does ST have ANY FAE's that can participate here? Can any Distributor FAE's lurking here participate?
Tips, buy me a coffee, or three.. PayPal Venmo Up vote any posts that you find helpful, it shows what's working..
zeus_zhn
Associate II
Posted on November 14, 2014 at 10:23

what solution do you have? How do you configure the DCMI_ESCR and DCMI_ESUR registers to let the DCMI can decode the ITU656 data?

Sebastian Gniazdowski
Associate III
Posted on January 13, 2017 at 14:56

TVP5150 output is a valid, standard one. You have considered order of fields in registers as order of codes in data stream – but that isn't related to each other. Just enter 'itu-r bt.656 eav sav' in google images to see that TVP5150 outputs according to the standard.

However, did anyone succeed in decoding video-decoder ICs? Not cameras?

Best regards,

Sebastian Gniazdowski