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- Joined: Wed Mar 26, 2014 4:53 pm
I am seeing a strange issue with 720p on Linux with respect to VANC caption data. The caption distribution packet (CDP) contains a sequence counter. We use that sequence counter as one check that the caption data we are receiving is good.
Our caption data occassionally is missing pairs or has "extra" pairs inserted. Corresponding to this, we receive video frames containing CDP's that are out of sequence. The sequence counter would indicate a previously received CDP. The sequence counter is off by 60 frames.
We are using the Decklink Quad card to capture 10-bit UYVY, then extracting the CDP's. We check for the DID/SID (61/01), checksum on the VANC packet, #User data words, CDP identifier (96 69), CDP checksum, and CDP sequence number - all appear okay except for the sequence number being out of sequence. We also grab the frameTime and hardware frame time from the IDeckLinkInputVideoFrame - the timestamps all indicate monotonically increasing frames - i.e. the timestamps do not "jump backwards".
Has anyone else noticed old ancillary data being delievered?
There are, of course, several possibilities:
1. The D/A feeding the card is delievering old CDP's.
2. The Quad card is delivering old CDP's.
3. Our software is somehow decoding old data.
Particulars:
Linux Fedora 20 3.13.10-200.fc20.x86_64
BIOS Information
Vendor: American Megatrends Inc.
Version: F9
Release Date: 09/19/2012
BIOS Revision: 4.6
Base Board Information
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: Z77-DS3H
DesktopVideo: desktopvideo-10.1-a11.x86_64
03:00.0 Multimedia video controller: Blackmagic Design DeckLink SDI/Duo/Quad (Quad card)
KiB Mem: 16323352 total, 14896840 used, 1426512 free, 323804 buffers
Thanks in advance,
Chuck
Our caption data occassionally is missing pairs or has "extra" pairs inserted. Corresponding to this, we receive video frames containing CDP's that are out of sequence. The sequence counter would indicate a previously received CDP. The sequence counter is off by 60 frames.
We are using the Decklink Quad card to capture 10-bit UYVY, then extracting the CDP's. We check for the DID/SID (61/01), checksum on the VANC packet, #User data words, CDP identifier (96 69), CDP checksum, and CDP sequence number - all appear okay except for the sequence number being out of sequence. We also grab the frameTime and hardware frame time from the IDeckLinkInputVideoFrame - the timestamps all indicate monotonically increasing frames - i.e. the timestamps do not "jump backwards".
Has anyone else noticed old ancillary data being delievered?
There are, of course, several possibilities:
1. The D/A feeding the card is delievering old CDP's.
2. The Quad card is delivering old CDP's.
3. Our software is somehow decoding old data.
Particulars:
Linux Fedora 20 3.13.10-200.fc20.x86_64
BIOS Information
Vendor: American Megatrends Inc.
Version: F9
Release Date: 09/19/2012
BIOS Revision: 4.6
Base Board Information
Manufacturer: Gigabyte Technology Co., Ltd.
Product Name: Z77-DS3H
DesktopVideo: desktopvideo-10.1-a11.x86_64
03:00.0 Multimedia video controller: Blackmagic Design DeckLink SDI/Duo/Quad (Quad card)
KiB Mem: 16323352 total, 14896840 used, 1426512 free, 323804 buffers
Thanks in advance,
Chuck