On Wed, 30 Jan 2013 01:23:48 +0100 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> wrote: > Hi Antonio, > Sorry for the delay Laurent and thanks for your reply, some more questions below. > On Monday 28 January 2013 13:22:10 Antonio Ospite wrote: > > Hi, > > > > looking at the MIPI Alliance Specification for Camera Serial Interface > > 2 (I'll call it MIPI-CSI2 from now on, the document I am referring to > > is mentioned at [1] and available at [2]), I see there is an YUV420 8 > > bit format (MIPI Data Type 0x18) specified with interleaved components > > in the form of: > > > > YYYY... (odd lines) > > UYVYUYVY... (even lines) > > > > With even lines twice the size of odd lines. > > Such format is also supported by some sensors, for instance ov5640, and > > by MIPI-CSI2 receivers like OMAP4 ISS. > > > > The doubt I have is: how should I represent those formats as media bus > > formats? > > We likely need new media bus formats to describe those. OK, I'll think to some names if I am going to actually use them. > > I've seen that some drivers (sensors and SoC, for instance[3]) tend to > > identify the MIPI-CSI2 format above (0x18) with media bus formats like > > V4L2_MBUS_FMT_UYVY8_1_5X8 (actually the code above uses > > V4L2_MBUS_FMT_YUYV8_1_5X8 is this OK?), but from the v4l2 documentation > > [4] I understand that this format is supposed to have data in this > > configuration: > > > > UUUU... > > YYYY... > > YYYY... > > VVVV... > > YYYY... > > YYYY... > > Not exactly, the UYVY8_1_5X8 is transmits Y, U and V samples as UYYVYY... > Wait, am I misunderstanding the documentation at http://kernel.org/doc/htmldocs/media/subdev.html#v4l2-mbus-pixelcode-yuv8 ? From the tables there it looks like that in UYVY8_1_5X8 the components are not interleaved on the same line, only the lines are. And that's why I was believing the code in [3] which maps YUYV8_1_5X8 (line interleaved, according to my interpretation of the v4l doc) to the MIPI-CSI2 0x18 format (components interleaved), was inaccurate (in the sense that I would have expected another [new] media bus format). > > That is with interleaved lines, but NOT interleaved components. Should > > new media bus formats be added for YYYY.../UYVYUYVY...? > > Yes, I think so. > > > Another doubt I have is: how is the YYYY.../UYVYUYVY... data supposed > > to be processed in userspace? Is the MIPI Receiver (i.e, the SoC) > > expected to be able to convert it to a more usable format like YUV420P > > or NV12/NV21? Or are there applications capable of handling this data > > directly, or efficiently convert them to planar or semi-planar YUV420 > > formats? > > The bridge (receiver and DMA engine) driver will expose V4L2 pixel formats > corresponding to the bridge capabilities. If the bridge can store the above > stream in memory in NV12 it will expose that to applications. If the bridge > stores data in memory as described above, it will just expose that format (it > seems to correspond to the V4L2 M420 pixel format), and applications will need > to handle that explicitly. > I see, so what I can get in userspace obviously depends on the hardware _and_ the driver (i.e. how complete it is in exposing the hardware capabilities), but that means that if a bridge can transparently pass the data it gets from the sensor (in a given mediabus format) we could have as many pixelformats as we have media bus formats, I know these latter won't be added in practice, but is my reasoning right in principle? Each mediabus format is a possible candidate for a new pixelformat. Maybe I am asking the obvious but I am trying to complete my understanding about the relationship between media bus formats and pixelformats. BTW that M420 format you mention is a bit different, from what I can see[6] it is something like a "line interleaved NV12": YYYY... YYYY... UVUV... YYYY... YYYY... UVUV... .... [6] http://www.linuxtv.org/downloads/v4l-dvb-apis/V4L2-PIX-FMT-M420.html So still another variation on the theme :) Or am I still reading the documentation the wrong way? > > In particular I am curios if the OMAP4 ISS can do the conversion to NV12, I > > understand that the formats with interleaved _lines_ can be produced by the > > resizer and handled by the OMAP ISP DMA-Engine by setting buffers offsets to > > Y and UV in order to send NV12 data to userspace, but I couldn't find info > > about how to handle the YUV420 MIPI-CSI2 formats (interleaved components) > > without the resizer in the Developer Manual [5]; having NV12 data directly > > from the hardware without using the OMAP4 ISS/ISP Resizer can be valuable in > > some use cases (e.g. dual camera setups). > > No idea about that, sorry. > Not at all. I was hoping Sergio would step up here. Thanks again, Antonio > > [1] http://www.mipi.org/specifications/camera-interface#CSI2 > > [2] http://ishare.sina.cn/dintro.php?id=20498632 > > [3] > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=driver > > s/media/platform/soc_camera/sh_mobile_csi2.c;h=a17aba9a0104c41cbc4e5e5d27701 > > 0ecac577600;hb=HEAD#l108 [4] > > http://kernel.org/doc/htmldocs/media/subdev.html#v4l2-mbus-pixelcode-yuv8 > > [5] http://www.ti.com/lit/ug/swpu235w/swpu235w.pdf > > -- > Regards, > > Laurent Pinchart > -- Antonio Ospite http://ao2.it A: Because it messes up the order in which people normally read text. See http://en.wikipedia.org/wiki/Posting_style Q: Why is top-posting such a bad thing? -- 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
