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| Who | What | When |
|---|---|---|
| javier__ | https://linuxtv.org/downloads/v4l-dvb-apis/uapi/v4l/pixfmt-007.html says that V4L2_COLORSPACE_SMPTE170M is the colorspace for SDTV and V4L2_COLORSPACE_REC709 for HDTV. But it seems drivers don't agree on the resolution that should be used as a threshold
some drivers set V4L2_COLORSPACE_REC709 for anything >= 720p while others use >= 576p sorry I meant > 570p | [13:48] |
| hverkuil | Older drivers often did it wrong. Some have been corrected but not all. | [13:51] |
| javier__ | hverkuil: so can I assume vivid does correctly then? (it also matches what gst does) | [13:51] |
| hverkuil | yes | [13:51] |
| javier__ | hverkuil: great, thanks a lot for the confirmation | [13:51] |
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| faLUCE | hello. When I get a packed video frame with the API, how are the pixels' BITS organized in bytes? For example, if I get a 16bits rgb pixel, how are 5-6-5 disposed into bytes? | [16:50] |
| pH5 | faLUCE: V4L2_PIX_FMT_RGB565 is not exactly well specified, but I think the common interpretation is the same as DRM_FORMAT_RGB565, which is little-endian, with R in the most significant bits: g[2:0]b[4:0] r[4:0]g[5:3]
faLUCE: see https://linuxtv.org/downloads/v4l-dvb-apis/uapi/v4l/pixfmt-packed-rgb.html?highlight=packed it is specified now. | [16:54] |
| faLUCE | pH5: in each case, one channel has a separate byte, right? There's not a case with one byte with two samples? b[0:3] b[4:7] ? | [16:56] |
| pH5 | well, blue is in the 5 lsb of the first byte in memory, red is in the 5 msb of the second byte in memory
green is spread over both bytes | [16:58] |
| faLUCE | pH5: then they are optimized considering a byte measure | [16:59] |
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| faLUCE | another question: does v4l have functions for reading PLANAR frames
? and storing the planes into nPlanes arrays ? | [17:56] |
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