TVP5158: TVP5158 about the image issues

Part Number: TVP5158

Hi Team,

The customer is using TVP5158. The issues are the displayed image always flashes and has the colored spots. The displayed image is in the image.

The schematic is also in the attach. Please check the attach.  The customer uses PAL-B, D, G, H, I standard. His screen resolution is 800x600@60Hz.

Here is his register configuration:

slaverAdr = 0xbe;

TVP5158_I2C_WriteByte(slaverAdr, 0xfe, 0x0f);

TVP5158_I2C_WriteByte(slaverAdr, 0x60, 0xb0);

TVP5158_I2C_WriteByte(slaverAdr, 0xa9, 0x04);

TVP5158_I2C_WriteByte(slaverAdr, 0xb0, 0x60); //4-channel pixel interleaved mode, 8bit BT656, D1 resolution

TVP5158_I2C_WriteByte(slaverAdr, 0xb2, 0x25);

TVP5158_I2C_WriteByte(slaverAdr, 0xb1, 0x17);

TVP5158_I2C_WriteByte(slaverAdr, 0x1a, 0xf0); //power down all audio ch

TVP5158_I2C_WriteByte(slaverAdr, 0xb4, 0xe4);

TVP5158_I2C_WriteByte(slaverAdr, 0x90, 0x10);

TVP5158_I2C_WriteByte(slaverAdr, 0x91, 0x80);

TVP5158_I2C_WriteByte(slaverAdr, 0x92, 0x80);

TVP5158_I2C_WriteByte(slaverAdr, 0x0e, 0x5F);

TVP5158_I2C_WriteByte(slaverAdr, 0x12, 0x03);

TVP5158_I2C_WriteByte(0xBE, 0xfe, 0x0f);

TVP5158_I2C_WriteByte(0xBE, 0x0d, 2);

For the customer's issue, can you give me some suggestions?

Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments

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3 Replies

  • These colored areas are a fundamental limit of composite video (CVBS).

    The way that color information is carried with CVBS is by using what is called a color sub-carrier signal and is a sine wave which is super-imposed on the luma part of the signal.

    What this means is that if you have high frequency luma e.g. (monochrome text) then there is no way to determine if this is high frequency text or color.

    The very first picture from this web page shows the issue very clearly...

    Some of these color artifacts can be mitigated by choosing a higher quality decoder (e.g. 3D comb filter) but these are a lot more expensive, more complex and are larger.

    See the following link for some information on various decoder qualities...

    The following article also shows some good examples...

    On a side note, the opposite also occurs, where chroma information is interpreted as luma. This results in "dot crawl" as discussed in the following link...

    Basically, trying to display computer graphics (i.e. high frequency transitions) using composite video is never going to look good.

    BR,

    Steve

    Please mark this post as answered via the Verify Answer button below if you think it answers your question.  Thanks!

  • In reply to Steve Clynes:

    Hi Steve,

    Thanks for your reply.

    Q1: You recommend the higher quality decoder, do we have this higher quality decoder?

    Q2: You mean that TVP5158 cannot achieve the customer's requirements?

    Q3: For the customer's issue, can you provide some specific solutions? For example, are the schematic and the register configurations correct?
  • In reply to Mickey Zhang:

    Q1) The TVP5147 will give better color separation. The TVP5160 will give excellent color separation. Neither of these devices are multi-channel decoders though.

    Q2) What ARE the customer requirements?

    Q3) As I mentioned this is a fundamental limitation of the decoder. Composite video is not designed to handle computer graphics. Is was designed for TV video.

    Please mark this post as answered via the Verify Answer button below if you think it answers your question.  Thanks!