Hi Kamil, On Tue, Mar 11, 2014 at 4:59 PM, Kamil Debski <k.debski@xxxxxxxxxxx> wrote: > Hi Arun, > >> From: Arun Kumar K [mailto:arunkk.samsung@xxxxxxxxx] On Behalf Of Arun >> Kumar K >> Sent: Friday, March 07, 2014 9:26 AM >> >> From: Pawel Osciak <posciak@xxxxxxxxxxxx> >> >> Currently, for formats that are not H264, MFC driver will check the >> consumed stream size returned by the firmware and, based on that, will >> try to decide whether the bitstream buffer contained more than one >> frame. If the size of the buffer is larger than the consumed stream, it >> assumes that there are more frames in the buffer and that the buffer >> should be resubmitted for decode. This rarely works though and actually >> introduces problems, because: >> >> - v7 firmware will always return consumed stream size equal to whatever >> the driver passed to it when running decode (which is the size of the >> whole buffer), which means we will never try to resubmit, because the >> firmware will always tell us that it consumed all the data we passed to >> it; > > This does sound like a hardware bug/feature. So in v7 the buffer is never > resubmitted, yes? And this patch makes no difference for v7? > To give some background to this - I have added this patch [1] so that multi-frame input buffer is supported by the driver. [1] https://patchwork.linuxtv.org/patch/15448/ This patch was added to address one test case in VP8 decoding where 2 frames used to come in a single buffer. Without this patch, it used to skip decoding of the 2nd frame even though firmware returned consumed bytes as only 1 frame size. Now this concept gave issues when we tried to decode the VP8 stream encoded using v7 firmware. In that case, an arbitrary amount of padding bytes were added by the firmware after every frame which is allowed as per VP8 standard. While decoding this using v6, firmware returns less consumed bytes than the input buffer, but the remaining bytes are just padding. So firmware used to throw error if we re-submit this stuffing bytes as a new frame. In v7 firmware, this problem doesnt exist as it consumes (atleast indicates that it consumed) all the input buffer. So we came to the conclusion that the testcase of giving multiple frames in one input buffer itself was wrong and hence it was removed. Now this concept is needed only for MPEG4 packed PB case which this code for resubmitting input buffer was meant for (before my patch made it generic). >> >> - v6 firmware will return the number of consumed bytes, but will not >> include the padding ("stuffing") bytes that are allowed after the frame >> in VP8. Since there is no way of figuring out how many of those bytes >> follow the frame without getting the frame size from IVF headers (or >> somewhere else, but not from the stream itself), the driver tries to >> guess that padding size is not larger than 4 bytes, which is not always >> true; > > How about v5 of MFC? I need to do some additional testing, as I don't want > to introduce any regressions. I remember that this check was a result of a > fair amount of work and testing with v5. > I hope it wont give any issues in v5 also as it was never meant to handle multiple frames in one input buffer. >> The only way to make it work is to queue only one frame per buffer from >> userspace and the check in the kernel is useless and wrong for VP8. >> MPEG4 still seems to require it, so keep it only for that format. > > Is your goal to give more than one frame in a single buffer and have the > buffer resubmitted? Or the opposite - you are getting the frame resubmitted > without the need? By the contents of this patch I guess the latter, on the > other hand I do remember that at some point the idea was to be able to queue > more than one frame per buffer. I don't remember exactly who was opting for > the ability to queue more frames in a single buffer... > I hope now it is clear. We want to disallow multiple frames in one buffer as the behavior is not consistent in v6 and its not allowed anyway from v7 onwards. Regards Arun > Best wishes, > -- > Kamil Debski > Samsung R&D Institute Poland > >> >> Signed-off-by: Pawel Osciak <posciak@xxxxxxxxxxxx> >> Signed-off-by: Arun Kumar K <arun.kk@xxxxxxxxxxx> >> --- >> drivers/media/platform/s5p-mfc/s5p_mfc.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc.c >> b/drivers/media/platform/s5p-mfc/s5p_mfc.c >> index e2aac59..66c1775 100644 >> --- a/drivers/media/platform/s5p-mfc/s5p_mfc.c >> +++ b/drivers/media/platform/s5p-mfc/s5p_mfc.c >> @@ -360,7 +360,7 @@ static void s5p_mfc_handle_frame(struct s5p_mfc_ctx >> *ctx, >> list); >> ctx->consumed_stream += s5p_mfc_hw_call(dev->mfc_ops, >> get_consumed_stream, dev); >> - if (ctx->codec_mode != S5P_MFC_CODEC_H264_DEC && >> + if (ctx->codec_mode == S5P_MFC_CODEC_MPEG4_DEC && >> ctx->consumed_stream + STUFF_BYTE < >> src_buf->b->v4l2_planes[0].bytesused) { >> /* Run MFC again on the same buffer */ >> -- >> 1.7.9.5 > -- 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
