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TVP5158 - (PAL SD) Poor video quality results ...

Other Parts Discussed in Thread: TVP5158

    Hello

 

    This message deals with the usage of the video ADC converter TVP5158. For the moment, the video quality (PAL SD) obtained does not fit our needs and we are unable to get better results despite our investigations. Until now, all our attempts to fix the problem led to failures, so I hope that someone will be inspired by this item.

     The test bench is made of a PAL equipment (BlurayDisc / DVD player) whose composite output is connected to the TVP5158 analog SD input. The TVP5158 feeds a Centaurus processor that de-interlaces the frames and then do a video loopback output to a display monitor (NB : test conditions).

     We use several video sequences to evaluate the video quality of the video chain. Amongst others, we can use a monochromatic chart and the colored top-level menu of the video player that also includes an area with a checkerboard made of different shades of grey. The dimension of the squares are quite small areas (the dimensions of the latter are several pixels long, so that it cannot be considered as a spatial frequency limitation / aliasing artifact). (As a point of comparison, we can point out that the reference video sequences sent directly by the player to the display monitor do not show any artifacts).

     Once the video has been digitalized by the TVP5158, the result displayed on the monitor shows the following

artifacts :

 -       Sharp edges in the original picture appear as blurred edges in the final picture. It looks like a sharp edge from black to white results in a wide trail of several pixels with different shades of grey as a transition in the horizontal and vertical directions.

          As a conclusion, text displays by the menu is almost unreadable :

          > e.g. : Lower case characters “e” and “c” appear as blurred “o”

          > e.g. : Upper case characters “C” appear as blurred “O”

 -       The checkerboard does not appear anymore and is replaced by a uniform single grey area.

      The same test has been run with the top-level menu of the video player, but with the TVP5158 device switched to a monochromatic mode via the settings of the TVP5158 registers. With luma component only (chroma components forced to 0 by the TVP5158 itself) the blurred artifacts remain the same.

 Our assumption is that something is wrongly configured in the TVP5158 registers, maybe one(several) default register(s) value(s) left unchanged that does(do) not fit our purpose. Despite all the customization settings we have tried (e.g. filters enabled/modified/disabled), nothing led up to an acceptable video quality at that point.

     Please let us know about any advice, reflection, comment (…). Any idea to investigate and go ahead will be really appreciated. Best regards.

                     Philippe

  • I would start by looking at the video capture buffer to determine if the is an source/capture issue or an output/display issue.

    Dump the VIP capture buffer to a file and examine the data (or use CCS/JTAG). You should be able to convert the luma channel to a bitmap fairly easily.

    If you have a logic analyzer available I would suggest also capturing the TVP output data and processing in a similar manner.

    Can you post a picture of what you are seeing ? I know quality will not be great but I would like to see the general scope of the issue. Pictures of the source when displayed on a monitor/TV would also help.

    BR,

    Steve

  • Hello Steve,

    First of all, I would like to apologize for the lack of activity since your last answer. The reason is that I have been involved in a task force to fix a bug for a critical project.

    Finally, I took few days this week to do more investigations and the good news seem to be that the TVP device is not the culprit. The problem seems to be the configuration or a bug in the Centaurus microprocessor : My last investigations led to the fact that the video capture module of the Centaurus only forwards even fields to its output;
    odd fields being lost/dropped ... So investigations are going on on the Centaurus side this time.

    Thanks for all. I have been very satisfied to see your reactivity to try to help me. Best regards.

                  Philippe

  • Philippe,

    Glad you have a good idea as to where the issue is most likely.

    Good lick clearing this issue.

    BR,

    Steve