On Mon, Jul 15, 2019 at 2:37 PM Hans Verkuil <hverk...@xs4all.nl> wrote: > > On 6/11/19 10:13 AM, Hans Verkuil wrote: > > On 6/9/19 4:38 PM, Maxime Jourdan wrote: > >> Hello, > >> > >> This RFC proposes a new format flag - V4L2_FMT_FLAG_DYN_RESOLUTION - used > >> to tag coded formats for which the device supports dynamic resolution > >> switching, via V4L2_EVENT_SOURCE_CHANGE. > >> This includes the initial "source change" where the device is able to > >> tell userspace about the coded resolution and the DPB size (which > >> sometimes translates to V4L2_CID_MIN_BUFFERS_FOR_CAPTURE). > > > > Shouldn't the initial source change still be there? The amlogic decoder > > is capable of determining the resolution of the stream, right? It just > > can't handle mid-stream changes. > > I've been thinking about this a bit more: there are three different HW > capabilities: > > 1) The hardware cannot parse the resolution at all and userspace has to tell > it > via S_FMT. > > 2) The hardware can parse the initial resolution, but is not able to handle > mid-stream resolution changes. > > 3) The hardware can parse the initial resolution and all following mid-stream > resolution changes. > > We can consider 2 the default situation. > > In case of 1 the SOURCE_CHANGE event is absent and userspace cannot subscribe > to it. Question: do we want to flag this with the format as well? I.e. with a > V4L2_FMT_FLAG_MANUAL_RESOLUTION? I think just not implementing the > SOURCE_CHANGE > event (and documenting this) is sufficient. >
I think that not implementing SOURCE_CHANGE is sufficient as well. The issue (in my case), is that the amlogic decoder _does_ support the event (case 3) for anything recent (H264, HEVC, VP9), but not for e.g MPEG 1/2 (case 1). A possible solution would be to create 2 separate devices, one implementing the event, the other not. Do you think this is reasonable ? This would discard the need for all the proposed flags, unless there are other decoder drivers that fall in case 2. > In case of 3 the format sets the V4L2_FMT_FLAG_DYN_RESOLUTION flag. > > What do you think? > > Regards, > > Hans > > > > > Regards, > > > > Hans > > > >> This flag is mainly aimed at stateful decoder drivers. > >> > >> This RFC is motivated by my development on the amlogic video decoder > >> driver, which does not support dynamic resolution switching for older > >> coded formats (MPEG 1/2, MPEG 4 part II, H263). It does however support > >> it for the newer formats (H264, HEVC, VP9). > >> > >> The specification regarding stateful video decoders should be amended > >> to include that, in the absence of this flag for a certain format, > >> userspace is expected to extract the coded resolution and allocate > >> a sufficient amount of capture buffers on its own. > >> I understand that this point may be tricky, since older kernels with > >> close-to-spec drivers would not have this flag available, yet would > >> fully support dynamic resolution switching. > >> However, with the spec not merged in yet, I wanted to have your opinion > >> on this late addition. > >> > >> The RFC patches also adds support for this flag for the 4 following > >> stateful decoder drivers: > >> - venus > >> - s5p-mfc > >> - mtk-vcodec > >> - vicodec > >> > >> Maxime Jourdan (5): > >> media: videodev2: add V4L2_FMT_FLAG_DYN_RESOLUTION > >> media: venus: vdec: flag OUTPUT formats with > >> V4L2_FMT_FLAG_DYN_RESOLUTION > >> media: s5p_mfc_dec: flag OUTPUT formats with > >> V4L2_FMT_FLAG_DYN_RESOLUTION > >> media: mtk-vcodec: flag OUTPUT formats with > >> V4L2_FMT_FLAG_DYN_RESOLUTION > >> media: vicodec: flag vdec/stateful OUTPUT formats with > >> V4L2_FMT_FLAG_DYN_RESOLUTION > >> > >> Documentation/media/uapi/v4l/vidioc-enum-fmt.rst | 7 +++++++ > >> drivers/media/platform/mtk-vcodec/mtk_vcodec_dec.c | 4 ++++ > >> drivers/media/platform/mtk-vcodec/mtk_vcodec_drv.h | 1 + > >> drivers/media/platform/qcom/venus/core.h | 1 + > >> drivers/media/platform/qcom/venus/vdec.c | 11 +++++++++++ > >> drivers/media/platform/s5p-mfc/s5p_mfc_common.h | 1 + > >> drivers/media/platform/s5p-mfc/s5p_mfc_dec.c | 13 +++++++++++++ > >> drivers/media/platform/vicodec/vicodec-core.c | 2 ++ > >> include/uapi/linux/videodev2.h | 5 +++-- > >> 9 files changed, 43 insertions(+), 2 deletions(-) > >> > > >
