Am 27.09.2012 15:20, schrieb Frank Schäfer: > Hi, > > Am 27.09.2012 12:26, schrieb Hans de Goede: >> Hi, >> >> On 09/26/2012 11:04 PM, Frank Schäfer wrote: >>> Hi, >>> >>> I've noticed the following issues/bugs while playing with qv4l: >>> 1.) with pac7302-webcams, only the RGB3 (RGB24) format is working. BGR3, >>> YU12 and YV12 are broken >>> 2.) for upside-down-mounted devices with an entry in libv4lconvert, >>> automatic h/v-flipping doesn't work with some formats >>> >>> I've been digging a bit deeper into the code and it seems that both >>> issues are caused by a problem with the libv4lconvert-API: >>> Besides image format conversion, function v4lconvert_convert() also does >>> the automatic image flipping and rotation (for devices with flags >>> V4LCONTROL_HFLIPPED, V4LCONTROL_VFLIPPED and V4LCONTROL_ROTATED_90_JPEG) >>> The problem is, that this function can be called multiple times for the >>> same frame, which then of course results in repeated flipping and >>> rotation... >>> >>> And this is exactly what happens with qv4l2: >>> qv4l2 gets the frame from libv4l2, which calls v4lconvert_convert() in >>> v4l2_dequeue_and_convert() or v4l2_read_and_convert(). >>> The retrieved frame has the requested format and is already >>> flipped/rotated. >>> qv4l2 then calls v4lconvert_convert() again directly to convert the >>> frame to RGB24 for GUI-output and this is where things are going wrong. >>> In case of h/v-flip, the double conversion "only" equalizes the >>> V4LCONTROL_HFLIPPED, V4LCONTROL_VFLIPPED flags, but for rotated devices, >>> the image gets corrupted. >>> >>> Sure, what qv4l2 does is a crazy. Applications usually request the >>> format needed for GUI-output directly from libv4l2. >>> Anyway, as long as it is valid to call libv4lconvert directly, we can >>> not assume that v4lconvert_convert() is called only one time. >>> >>> At the moment, I see no possibility to fix this without changing the >>> libv4lconvert-API. >>> Thoughts ? >> What you've found is a qv4l2 bug (do you have the latest version?) > Of course, I'm using the latest developer version. > > Even if this is just a qv4l2-bug: how do you want to fix it without > removing the format selction feature ? > >> one >> is supposed to either use libv4l2, or do raw device access and then >> call libv4lconvert directly. > Even when using libv4lconvert only, multiple frame conversions are still > causing the same trouble. > > Hans, first of all, I would like to say that my intention is not to > savage your work. > I know API design and maintanance is very difficult and you are doing a > great job. > Things like this just happen and we have to make the best out of it. > > But saying that libv4l2 and libv4lconvert can't be used at the same > (although they are separate public libraries) and that > v4lconvert_convert() may only be called once per frame seems to me like > a - I would say "weird" - reinterpretation of the API... > I don't think this is what applications currently expect (qv4l2 doesn't > ;) ) and at least this would need public clarification. > > So let's see if there is a possibility to fix the issue by improving the > libraries without breaking the API. > > What about the following solution: > - make v4lconvert_convert_pixfmt() and v4lconvert_crop() public > functions and fix qv4l2 to use them instead of v4lconvert_convert() > - also make the flip and rotation functions (v4lconvert_flip(), > v4lconvert_rotate90()) publicly available > - modify libv4l2 to call v4lconvert_convert_pixfmt() and the > flip+rotation+crop functions instead of v4lconvert_convert() > - fix v4lconvert_convert() to not do transparent image flipping/rotation > (means => call v4lconvert_convert_pixfmt() and v4lconvert_crop() only). No, of course we can't do that... So let's leave v4lconvert_convert() as broken as it is and just mark it as deprecated. The rest should work. Frank > For API-clean-up: > - create a copy of (the fixed) v4lconvert_convert() called something > like v4lconvert_convert_crop() > - declare v4lconvert_convert() as deprecated so that we can remove it > sometime in the future > > What do you think ? > > Regards, > Frank > > > >> These are also the 2 modes qv4l2 has >> (for testing purposes), it is not supposed to do the manual convert call >> when using libv4l2 to access the device ... >> >> Regards, >> >> Hans -- 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
