On 05/09/2018 04:11 PM, Mark Thompson wrote:
On 09/05/18 08:57, Jorge Ramirez-Ortiz wrote:
On 05/09/2018 01:33 AM, Mark Thompson wrote:
diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c
index ed5193ecc1..2b33badb08 100644
--- a/libavcodec/v4l2_m2m_dec.c
+++ b/libavcodec/v4l2_m2m_dec.c
@@ -23,12 +23,18 @@
#include <linux/videodev2.h>
#include <sys/ioctl.h>
+
+#include "libavutil/hwcontext.h"
+#include "libavutil/hwcontext_drm.h"
#include "libavutil/pixfmt.h"
#include "libavutil/pixdesc.h"
#include "libavutil/opt.h"
#include "libavcodec/avcodec.h"
#include "libavcodec/decode.h"
+#include "libavcodec/hwaccel.h"
+#include "libavcodec/internal.h"
+
#include "v4l2_context.h"
#include "v4l2_m2m.h"
#include "v4l2_fmt.h"
@@ -183,6 +189,15 @@ static av_cold int v4l2_decode_init(AVCodecContext *avctx)
capture->av_codec_id = AV_CODEC_ID_RAWVIDEO;
capture->av_pix_fmt = avctx->pix_fmt;
+ /* the client requests the codec to generate DRM frames:
+ * - data[0] will therefore point to the returned AVDRMFrameDescriptor
+ * check the ff_v4l2_buffer_to_avframe conversion function.
+ * - the DRM frame format is passed in the DRM frame descriptor layer.
+ * check the v4l2_get_drm_frame function.
+ */
+ if (avctx->pix_fmt == AV_PIX_FMT_DRM_PRIME)
+ s->output_drm = 1;
+
ret = ff_v4l2_m2m_codec_init(avctx);
if (ret) {
av_log(avctx, AV_LOG_ERROR, "can't configure decoder\n");
@@ -202,6 +217,11 @@ static const AVOption options[] = {
{ NULL},
};
As a follow up to your comment on pixel format negotiation
(AvCodecContext.getformat), notice that this is a tentative request from the
user to select a pixel format.
The actual pixel format negotiation - where the decoder will select the pixel
format- will happen later during v4l2_try_start.
Indeed. get_format() will have to be called during the pixel format
negotiation so that the user can pick between whatever the supported software
format is (NV12, NV21, YUV420P P010, whatever) or the DRM-PRIME object hardware
format (if supported).
but in the use case that we are trying to implement, it is the user -
not the codec - the one that has to specifically request DRM support to
libavcodec since the v4l2m2m decoder can provide either of them
indistinctly.
it is just not clear to me how the libavcodec client can request the DRM
pix_fmt if not tentatively setting the pix_fmt during v4l2_decode_init.
AVCodecContext.pix_fmt is intended to be set by the decoder to say what pix_fmt
it intends to produce (though even in that role it's highly dubious given
threaded decoders and stream changes). For historical reasons it is also
allowed to be set externally (because of libavformat interactions), but this
shouldn't be used for configuration.
This change enables the v4l2m2m decoder to output either dmabuf descriptors to
be consumed by a DRM or video frame formats to be consumed by SDL (for
instance).
As an example, these changes have been tested with ffplay (SDL based display)
and a simple DRM application [1]
Lukas tested with other tools.
[1]https://github.com/baylibre/ffmpeg-drm
We should make this usable in the ffmpeg application too. The DRM object
format is works fine in ffmpeg already with Rockchip decoder (consumed by the
hwmap/hwdownload filters, or by mapping to OpenCL), but that doesn't need the
format selection part. (There are also kmsgrab and VAAPI, but those aren't
making DRM PRIME frames directly at a decoder.) I believe this should be
straightforward with a small modification to get_format() in ffmpeg.c to accept
AV_CODEC_HW_CONFIG_METHOD_INTERNAL, I can look at this once we have a codec
which will need it.
so what would be the sequence of calls for an libavcodec client to
request the DRM format?
https://github.com/BayLibre/ffmpeg-drm/blob/master/main.c#L598
- Mark
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