Hi Hans, Am Dienstag, den 30.09.2014, 15:43 +0200 schrieb Hans Verkuil: > On 09/30/14 11:57, Philipp Zabel wrote: > > Hi, > > > > These patches add JPEG encoding and decoding support for CODA7541 (i.MX5). > > The encoder video device is split into one video device per codec, so that > > each video device can register only the relevant controls. The H.264/MPEG4 > > decoder is kept as one video device, but the JPEG decoder video device is > > separate because it supports more uncompressed formats (currently YUV422P, > > in the future grayscale or YUV 4:4:4 support could be added). > > Normally device nodes are linked to DMA engines, so the only reason why you > would have e.g. two video nodes is if you can capture from both at the same > time. Is that the case here as well? If not, then it really should be a > single video node. That not all controls are relevant for the currently > chosen codec is not important. > > Are there other reasons than the controls to split it up into multiple video > devices? I had already split the encoder and decoder parts of this mem2mem device into two video devices because of the issue of changing available capture formats depending on the selected output format. The motivation for splitting the JPEG codecs from the H264/MPEG4 codecs is the same: to avoid the appearing and disappearing of the YUV422P format on the uncompressed side whenever the compressed format changes between JPEG and H264/MPEG4. I could keep the H264 and MPEG4 encoders combined without running into this issue. Furthermore, I want to change the output queue for the currently available decoders to use vb2-vmalloc eventually (because the CPU has to copy incoming frames into the bitstream buffer), but have to keep using vb2-dma-contig for the CODA960 JPEG decoder, which will have the hardware read from the incoming buffers directly. regards Philipp -- 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
