I'm trying to decode video signals with TVP5146M2 also in lines 6 to 22 for a PAL signal.
The result is a very noisy signal.
In the attached zip file you can see the capture of the same signal in line 17 and in line 81.
The attached zip file containes also the file with the dump of TVP5146M2 registers.
There is something to change in order to decode correctly video signals in the "teletext" lines?
I've seen some enhancement if I don't use the comb filter, but this lead to worse signal decoding for all lines.
In the pictures the green line represent Y samples, the red one the Cr samples and th blu te Cb samples.
The situation depicted in these figures happens when lines near 17 and 18 carry teletext signals. if there is no teletext in tjhe other lines the situation get better; in any the "noise" remains.
If I declare these lines as RAW the samples are OK (obviously also Cr and Cb signals carry Y information): no "noise" on signals.
It seems that on line 22 the decoding is carried out correctly.
Has anyone experienced such a strange behaviour?
This issue is of great importance for our product.
Is there anyone that can answer to my problem?
We need a urgent solution, and if it is not possible with TVP5146 we are planning to use a chip from other suppliers.
I’m waiting for a reply.
Are the noisy lines related to the VBLK interval that is progammed? If you change the VBLK stop register, does the last noisy line change?
It is possible that the YC separation and processing is different duing the VBLK interval.
No, the behavior is independent from the VBLK settings.
We suspect that some of the video processing, perhaps comb filter, is disabled during the vertical balnking interval. Using raw data mode duing vertical blanking may be your best option to provide the cleanest output for external teletext processing.
Yes, for teletext raw processing is good.
But it is not for VITS, expecially for the signal for DGDP, usually in line 330 for PAL: it contains a luminance staircase from black to white, with constant crominance suiperimposed.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.