Am 27.09.2012 16:47, schrieb Hans Verkuil: > On Thu 27 September 2012 15:20:21 Frank Schäfer wrote: >> 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. > qv4l2 will do things the way you expect if you open the video node in 'raw' > mode (i.e. without using libv4l2), either through the File menu or by adding > the -r option: qv4l2 -r /dev/video0 Yes, in raw mode it should work (didn't test). > BTW, which pixelformat do you select? I think that if you select RGB24, then > no extra conversion step will take place. That's what I said. > Note that qv4l2 is primarily meant for testing. Normal applications will never > call v4lconvert_convert(). I remember having seen one, but I can't remember details :( Last application I've sent patches for was Kopete, but that one only uses libv4l2 (don't look into its video code, it still makes you blind !) :( Anyway, it's a public API and therefore we have to assume that applications are using it. ;) > That said, qv4l2 has the potential of becoming a much more usable application > if someone would be interested in putting some more work into it. I agree, it has potential. And the current version has gained some nice features ! Maybe I will send some patches in the future. > >>>> 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). >> 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 > As qv4l2 maintainer Sorry, I didn't notice that. I thought Hans (de Goede) is the maintainer for the whole v4l-utils... > I would definitely be interested in seeing this happen. > On the other hand, qv4l2 is an unusual application. Normal apps are unlikely > to use this feature, although I can imagine it being used in some embedded > environments. Well, first priority is to fix the API with its current functionality. But you are right, this would also provide new possibilities for applications. For example: with a publicly available function v4lconvert_rotate() runtime image rotation can be implemented easily by applications. Oh, and yes, I would do the work ;) But we need a sane plan first. And we should think about it twice... Regards, Frank > Regards, > > Hans V. > >> 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 >> -- 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
