[libcamera-devel] [PATCH v3 1/1] pipeline: raspberrypi: Fix handling of colour spaces

[Kieran Bingham]

Hi David,

There's a small question below that is holding this back from being merged.

I'm planning a release tomorrow, so I'd like to get this colourspace fix
in.

Quoting Umang Jain via libcamera-devel (2023-01-25 06:48:19)
> Hi David,
> 
> On 1/20/23 9:52 PM, David Plowman via libcamera-devel wrote:
> > We implement a custom validateColorSpaces method that forces all
> > (non-raw) streams to same colour space, whilst distinguishing RGB
> > streams from YUV ones, as the former must have the YCbCr encoding and
> > range over-written.
> >
> > When we apply the colour space, we always send the full YUV version as
> > that gets converted correctly to what our hardware drivers expect. It
> > is also careful to check what comes back as the YCbCr information gets
> > overwritten again on the way back.
> >
> > Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> > Reviewed-by: Naushir Patuck <naush at raspberrypi.com>
> > ---
> >   .../pipeline/raspberrypi/raspberrypi.cpp      | 115 +++++++++++++++++-
> >   1 file changed, 114 insertions(+), 1 deletion(-)
> >
> > diff --git a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > index 8569df17..f768dced 100644
> > --- a/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > +++ b/src/libcamera/pipeline/raspberrypi/raspberrypi.cpp
> > @@ -310,6 +310,7 @@ class RPiCameraConfiguration : public CameraConfiguration
> >   public:
> >       RPiCameraConfiguration(const RPiCameraData *data);
> >   
> > +     CameraConfiguration::Status validateColorSpaces(ColorSpaceFlags flags);
> >       Status validate() override;
> >   
> >       /* Cache the combinedTransform_ that will be applied to the sensor */
> > @@ -317,6 +318,13 @@ public:
> >   
> >   private:
> >       const RPiCameraData *data_;
> > +
> > +     /*
> > +      * Store the colour spaces that all our streams will have. RGB format streams
> > +      * will be the same but need the YCbCr fields cleared.
> 
> Would re-pharse it like:
> 
>          /*
>           * Store the colour spaces that all our streams will have. RGB 
> format streams
>           * will have the same colorspace as YUV streams, with YCbCr 
> field cleared and
>           * range set to full.
>           */

Are you happy with the expansion on this comment?


--
Kieran



> 
> > +      */
> > +     std::optional<ColorSpace> yuvColorSpace_;
> > +     std::optional<ColorSpace> rgbColorSpace_;
> >   };
> >   
> >   class PipelineHandlerRPi : public PipelineHandler
> > @@ -357,6 +365,105 @@ RPiCameraConfiguration::RPiCameraConfiguration(const RPiCameraData *data)
> >   {
> >   }
> >   
> > +static const std::vector<ColorSpace> validColorSpaces = {
> > +     ColorSpace::Sycc,
> > +     ColorSpace::Smpte170m,
> > +     ColorSpace::Rec709
> > +};
> > +
> > +static std::optional<ColorSpace> findValidColorSpace(const ColorSpace &colourSpace)
> > +{
> > +     for (auto cs : validColorSpaces) {
> > +             if (colourSpace.primaries == cs.primaries &&
> > +                 colourSpace.transferFunction == cs.transferFunction)
> > +                     return cs;
> > +     }
> > +
> > +     return std::nullopt;
> > +}
> > +
> > +static bool isRgb(const PixelFormat &pixFmt)
> > +{
> > +     const PixelFormatInfo &info = PixelFormatInfo::info(pixFmt);
> > +     return info.colourEncoding == PixelFormatInfo::ColourEncodingRGB;
> > +}
> > +
> > +static bool isYuv(const PixelFormat &pixFmt)
> > +{
> > +     /* The code below would return true for raw mono streams, so weed those out first. */
> > +     if (isRaw(pixFmt))
> > +             return false;
> > +
> > +     const PixelFormatInfo &info = PixelFormatInfo::info(pixFmt);
> > +     return info.colourEncoding == PixelFormatInfo::ColourEncodingYUV;
> > +}
> > +
> > +/*
> > + * Raspberry Pi drivers expect the following colour spaces:
> > + * - V4L2_COLORSPACE_RAW for raw streams.
> > + * - One of V4L2_COLORSPACE_JPEG, V4L2_COLORSPACE_SMPTE170M, V4L2_COLORSPACE_REC709 for
> > + *   non-raw streams. Other fields such as transfer function, YCbCr encoding and
> > + *   quantisation are not used.
> > + *
> > + * The libcamera colour spaces that we wish to use corresponding to these are therefore:
> > + * - ColorSpace::Raw for V4L2_COLORSPACE_RAW
> > + * - ColorSpace::Sycc for V4L2_COLORSPACE_JPEG
> > + * - ColorSpace::Smpte170m for V4L2_COLORSPACE_SMPTE170M
> > + * - ColorSpace::Rec709 for V4L2_COLORSPACE_REC709
> > + */
> 
> Thank you for the information. This makes the expectations clearer.
> 
> With that,
> 
> Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>
> 
> 
> I can fixup the comment while applying the patch (if you are OK with the 
> comment's explanation).
> 
> > +
> > +CameraConfiguration::Status RPiCameraConfiguration::validateColorSpaces([[maybe_unused]] ColorSpaceFlags flags)
> > +{
> > +     Status status = Valid;
> > +     yuvColorSpace_.reset();
> > +
> > +     for (auto cfg : config_) {
> > +             /* First fix up raw streams to have the "raw" colour space. */
> > +             if (isRaw(cfg.pixelFormat)) {
> > +                     /* If there was no value here, that doesn't count as "adjusted". */
> > +                     if (cfg.colorSpace && cfg.colorSpace != ColorSpace::Raw) {
> > +                             status = Adjusted;
> > +                             cfg.colorSpace = ColorSpace::Raw;
> > +                     }
> > +                     continue;
> > +             }
> > +
> > +             /* Next we need to find our shared colour space. The first valid one will do. */
> > +             if (cfg.colorSpace && !yuvColorSpace_)
> > +                     yuvColorSpace_ = findValidColorSpace(cfg.colorSpace.value());
> > +     }
> > +
> > +     /* If no colour space was given anywhere, choose sYCC. */
> > +     if (!yuvColorSpace_)
> > +             yuvColorSpace_ = ColorSpace::Sycc;
> > +
> > +     /* Note the version of this that any RGB streams will have to use. */
> > +     rgbColorSpace_ = yuvColorSpace_;
> > +     rgbColorSpace_->ycbcrEncoding = ColorSpace::YcbcrEncoding::None;
> > +     rgbColorSpace_->range = ColorSpace::Range::Full;
> > +
> > +     /* Go through the streams again and force everyone to the same colour space. */
> > +     for (auto cfg : config_) {
> > +             if (cfg.colorSpace == ColorSpace::Raw)
> > +                     continue;
> > +
> > +             if (isYuv(cfg.pixelFormat) && cfg.colorSpace != yuvColorSpace_) {
> > +                     /* Again, no value means "not adjusted". */
> > +                     if (cfg.colorSpace)
> > +                             status = Adjusted;
> > +                     cfg.colorSpace = yuvColorSpace_;
> > +             }
> > +             if (isRgb(cfg.pixelFormat) && cfg.colorSpace != rgbColorSpace_) {
> > +                     /* Be nice, and let the YUV version count as non-adjusted too. */
> > +                     if (cfg.colorSpace && cfg.colorSpace != yuvColorSpace_)
> > +                             status = Adjusted;
> > +                     cfg.colorSpace = rgbColorSpace_;
> > +             }
> > +     }
> > +
> > +     return status;
> > +}
> > +
> >   CameraConfiguration::Status RPiCameraConfiguration::validate()
> >   {
> >       Status status = Valid;
> > @@ -533,7 +640,8 @@ CameraConfiguration::Status RPiCameraConfiguration::validate()
> >               V4L2DeviceFormat format;
> >               format.fourcc = dev->toV4L2PixelFormat(cfg.pixelFormat);
> >               format.size = cfg.size;
> > -             format.colorSpace = cfg.colorSpace;
> > +             /* We want to send the associated YCbCr info through to the driver. */
> > +             format.colorSpace = yuvColorSpace_;
> >   
> >               LOG(RPI, Debug)
> >                       << "Try color space " << ColorSpace::toString(cfg.colorSpace);
> > @@ -542,6 +650,11 @@ CameraConfiguration::Status RPiCameraConfiguration::validate()
> >               if (ret)
> >                       return Invalid;
> >   
> > +             /*
> > +              * But for RGB streams, the YCbCr info gets overwritten on the way back
> > +              * so we must check against what the stream cfg says, not what we actually
> > +              * requested (which carefully included the YCbCr info)!
> > +              */
> >               if (cfg.colorSpace != format.colorSpace) {
> >                       status = Adjusted;
> >                       LOG(RPI, Debug)
>