On 10/04/2017 06:23 PM, Mark Thompson wrote:
On 04/10/17 16:48, Jorge Ramirez-Ortiz wrote:
On 10/04/2017 11:28 AM, Jorge Ramirez-Ortiz wrote:
On 10/04/2017 11:23 AM, wm4 wrote:
On Wed, 4 Oct 2017 11:17:24 +0200
Jorge Ramirez-Ortiz <jorge.ramirez-or...@linaro.org> wrote:
Some V4L2 drivers fail to allocate buffers when sizeimage is not set
to a max value. This is indeed the case for sp5-mfc [1]
Most drivers should be able to calculate this value from the frame
dimensions and format - or at least have their own default.
However since this work around should not impact those drivers doing
the "right thing" this commit just provides such a default.
[1] linux.git/drivers/media/platform/s5p-mfc
---
libavcodec/v4l2_context.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/libavcodec/v4l2_context.c b/libavcodec/v4l2_context.c
index 297792f..2707ef5 100644
--- a/libavcodec/v4l2_context.c
+++ b/libavcodec/v4l2_context.c
@@ -92,6 +92,8 @@ static inline int v4l2_type_supported(V4L2Context *ctx)
static inline void v4l2_save_to_context(V4L2Context* ctx, struct
v4l2_format_update *fmt)
{
+ const int MAX_SIZEIMAGE = 2 * 1024 * 1024;
+
ctx->format.type = ctx->type;
if (fmt->update_avfmt)
@@ -101,13 +103,21 @@ static inline void v4l2_save_to_context(V4L2Context* ctx,
struct v4l2_format_upd
/* update the sizes to handle the reconfiguration of the capture
stream at runtime */
ctx->format.fmt.pix_mp.height = ctx->height;
ctx->format.fmt.pix_mp.width = ctx->width;
- if (fmt->update_v4l2)
+ if (fmt->update_v4l2) {
ctx->format.fmt.pix_mp.pixelformat = fmt->v4l2_fmt;
+
+ /* s5p-mfc requires the user to specify MAX buffer size */
+ ctx->format.fmt.pix_mp.plane_fmt[0].sizeimage = MAX_SIZEIMAGE;
+ }
} else {
ctx->format.fmt.pix.height = ctx->height;
ctx->format.fmt.pix.width = ctx->width;
- if (fmt->update_v4l2)
+ if (fmt->update_v4l2) {
ctx->format.fmt.pix.pixelformat = fmt->v4l2_fmt;
+
+ /* s5p-mfc requires the user to specify MAX buffer size */
+ ctx->format.fmt.pix.sizeimage = MAX_SIZEIMAGE;
+ }
}
}
Isn't this something that should be fixed in the driver?
yes but it might take forever and I dont know how many other drivers might need
it.
Why 2MB?
no analysis done but seems to be enough to hold an encoded frame. Should it be
any bigger?
I could use the calculations below if a generic magic number is a problem:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/platform/qcom/venus/venc.c#n52
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/media/platform/qcom/venus/vdec.c#n49
please let me know
I think you are doing the same thing here as
<http://git.videolan.org/?p=ffmpeg.git;a=blob;f=libavcodec/vaapi_encode.c;h=e13e99587dff35b1aa72f8d50f8da03cf4ffbb6e;hb=HEAD#l1239>.
The fixed 2MB feels likely to be too low for high-bandwidth video - you only need
480Mbps at 30fps to make frames which are 2MB *on average*, with intra frames being
larger.
ah ok. thanks for the info!
The calculated numbers for Qualcomm are probably fine, but do consider the
possible failure modes - what would happen if it were exceeded? (For H.264 at
least you might be able to invoke the level restriction on minimum-compression
to say that doesn't happen, but I don't know about other cases.)
sure. that can only happen at runtime - not when buffers are being requested -
so the v4l2 the driver would report the error back to ffmpeg; and this error
(like any other error from the driver) is handled with the current framework so
I believe we are safe.
In any case, please add a comment to say where whatever number you use came
from.
ok.
- Mark
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