While there is already a comment about the always_needs_conversion
logic at libv4lconvert, the comment is not clear enough. Also,
the decision of needing a conversion or not is actually at the
supported_src_pixfmts[] table.
Improve the comments to make it clearer about what criteria should be
used with regards to exposing formats to userspace.
Suggested-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
---
lib/libv4lconvert/libv4lconvert.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/lib/libv4lconvert/libv4lconvert.c b/lib/libv4lconvert/libv4lconvert.c
index da718918b030..2718446ff239 100644
--- a/lib/libv4lconvert/libv4lconvert.c
+++ b/lib/libv4lconvert/libv4lconvert.c
@@ -74,8 +74,15 @@ const struct libv4l_dev_ops *v4lconvert_get_default_dev_ops()
static void v4lconvert_get_framesizes(struct v4lconvert_data *data,
unsigned int pixelformat, int index);
-/* Note for proper functioning of v4lconvert_enum_fmt the first entries in
- supported_src_pixfmts must match with the entries in supported_dst_pixfmts */
+/*
+ * Notes:
+ * 1) for proper functioning of v4lconvert_enum_fmt the first entries in
+ * supported_src_pixfmts must match with the entries in
+ * supported_dst_pixfmts.
+ * 2) The field needs_conversion should be zero, *except* for device-specific
+ * formats, where it doesn't make sense for applications to have their
+ * own decoders.
+ */
#define SUPPORTED_DST_PIXFMTS \
/* fourcc bpp rgb yuv needs */ \
/* rank rank conversion */ \
@@ -175,9 +182,13 @@ struct v4lconvert_data *v4lconvert_create_with_dev_ops(int fd, void *dev_ops_pri
int i, j;
struct v4lconvert_data *data = calloc(1, sizeof(struct v4lconvert_data));
struct v4l2_capability cap;
- /* This keeps tracks of devices which have only formats for which apps
- most likely will need conversion and we can thus safely add software
- processing controls without a performance impact. */
+ /*
+ * This keeps tracks of device-specific formats for which apps most
+ * likely don't know. If all a driver can offer are proprietary
+ * formats, a conversion is needed anyway. We can thus safely
+ * add software processing controls without much concern about a
+ * performance impact.
+ */
int always_needs_conversion = 1;
if (!data) {
--
2.9.3
