Hi Sakari, On Thu, Sep 13, 2012 at 6:29 AM, Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hi Sakari, > > On Friday 07 September 2012 21:46:44 Sakari Ailus wrote: >> >> Could you replace the above with this text (with appropriate indentation >> etc.) while keeping the reference to Wikipedia? >> >> ------8<------ >> Differential pulse-code modulation (DPCM) compression can be used to >> compress the samples into fewer bits than they would otherwise require. >> This is done by calculating the difference between consecutive samples >> and outputting the difference which in average is much smaller than the >> values of the samples themselves since there is generally lots of >> correlation between adjacent pixels. In decompression the original >> samples are reconstructed. The process isn't lossless as the encoded >> sample size in bits is less than the original. >> >> Formats using DPCM compression include <xref >> linkend="pixfmt-srggb10dpcm8" />. >> >> This control is used to select the predictor used to encode the samples. > > If I remember correctly this control will be used on the receiver side on > DaVinci, to decode pixels not encode them. How is the predictor used in that > case ? Must it match the predictor used on the encoding side ? If so I expect > documentation to be available somewhere. > > The OMAP3 ISP supports both DPCM encoding and decoding, and documents the > predictors as > > "- The simple predictor > > This predictor uses only the previous same color component value as a > prediction value. Therefore, only two-pixel memory is required. > > - The advanced predictor > > This predictor uses four previous pixel values, when the prediction value is > evaluated. This means that also the other color component values are used, > when the prediction value has been defined." > > It also states the the simple predictor is preferred for 10-8-10 conversion, > and the advanced predictor for 10-7-10 and 10-6-10 conversion. > What do you suggest ? Regards, --Prabhakar Lad >> The main difference between the simple and the advanced predictors is >> image quality, with advanced predictor supposed to produce better >> quality images as a result. Simple predictor can be used e.g. for >> testing purposes. >> ------8<------ > > -- > Regards, > > Laurent Pinchart > > _______________________________________________ > Davinci-linux-open-source mailing list > Davinci-linux-open-source@xxxxxxxxxxxxxxxxxxxx > http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
