On 12/15/24 22:15, Zhao Zhili wrote:
On Dec 15, 2024, at 12:14, Scott Theisen<scott.the....@gmail.com> wrote:
Based on patches by Lukas Rusak from
https://github.com/lrusak/FFmpeg/commits/v4l2-drmprime-v4
libavcodec: v4l2m2m: output AVDRMFrameDescriptor
https://github.com/lrusak/FFmpeg/commit/2cb8052ac65a56d8a3f347a1e6f12d4449a5a614
libavcodec: v4l2m2m: depends on libdrm
https://github.com/lrusak/FFmpeg/commit/ab4cf3e6fb37cffdebccca52e36a7b2deb7e729f
libavcodec: v4l2m2m: set format_modifier to DRM_FORMAT_MOD_LINEAR
https://github.com/lrusak/FFmpeg/commit/9438a6efa29c7c7ec80c39c9b013b9a12d7b5f33
libavcodec: v4l2m2m: only mmap the buffer when it is output type and drm prime
is used
https://github.com/lrusak/FFmpeg/commit/093656607863e47630de2d1cfcf0ac8e4b93a69e
libavcodec: v4l2m2m: allow using software pixel formats
https://github.com/lrusak/FFmpeg/commit/8405b573e83838e6b2fea99825fbef32ee9f7767
libavcodec: v4l2m2m: implement hwcontext
https://github.com/lrusak/FFmpeg/commit/b2c1f1eb39b54bf034497a7f2a7f23855d0a7cde
libavcodec: v4l2m2m: implement flush
https://github.com/lrusak/FFmpeg/commit/e793ef82727d6d6f55c40844463d476e7e84efad
Originally added to MythTV in:
FFmpeg: Patch FFmpeg for V4L2 codecs DRM PRIME support
https://github.com/MythTV/mythtv/commit/cc7572f9b26189ad5d5d504c05f08e53e4e61b54
FFmpeg: Re-apply v4l2 memory to memory DRM_PRIME support
https://github.com/MythTV/mythtv/commit/1c942720591b5b7820abe9ed0d805afabbdffe3c
modified in:
V4L2 Codecs: Fix lockup when seeking
https://github.com/MythTV/mythtv/commit/fdc0645aba9a9ad373888bd62ebcbc83a3feb7e5
v4l2_buffers: Add some libdrm ifdef's
https://github.com/MythTV/mythtv/commit/336df1067abfa4fe7cf611541e5b6f3561fc81a2
!!!!
NB: libavcodec/v4l2_m2m_dec.c: v4l2_decode_init(): I'm returning -1
since I don't know what error code I should use.
Note also Lucas Rusak's v5 series:
closer diff to current state, otherwise unchanged
libavcodec: v4l2m2m: output AVDRMFrameDescriptor
https://github.com/lrusak/FFmpeg/commit/c6b85ed30f06ea99513b13cc768a922ebe4d68c2
new option:
libavcodec: v4l2m2m: add option to specify pixel format used by the decoder
https://github.com/lrusak/FFmpeg/commit/ffc4419f456c00ab71cf93f792b0473c6de14e64
additional code vs v4
libavcodec: v4l2m2m: implement flush
https://github.com/lrusak/FFmpeg/commit/8595d06d4909bbec0aa14625fcfc869c6bcef696
---
configure | 1 +
libavcodec/v4l2_buffers.c | 206 +++++++++++++++++++++++++++++++++++---
libavcodec/v4l2_buffers.h | 4 +
libavcodec/v4l2_context.c | 43 +++++++-
libavcodec/v4l2_context.h | 2 +
libavcodec/v4l2_m2m.h | 5 +
libavcodec/v4l2_m2m_dec.c | 62 ++++++++++++
7 files changed, 305 insertions(+), 18 deletions(-)
diff --git a/configure b/configure
index bf55ba67fa..5f02cf3b51 100755
--- a/configure
+++ b/configure
@@ -3770,6 +3770,7 @@ sndio_indev_deps="sndio"
sndio_outdev_deps="sndio"
v4l2_indev_deps_any="linux_videodev2_h sys_videoio_h"
v4l2_indev_suggest="libv4l2"
+v4l2_outdev_deps="libdrm"
Why v4l2_outdev when the patch is for libavcodec?
Lukas Rusak appears to have only submitted up to v3 of his patches in 2018.
This appears to be from a comment in
https://patchwork.ffmpeg.org/project/ffmpeg/patch/4bbeff66-6123-9296-5775-96d75809e...@jkqxz.net/
However, with the `#if CONFIG_LIBDRM`s added by Mark Kendall for MythTV,
I don't think it is a hard dependency.
...
diff --git a/libavcodec/v4l2_m2m_dec.c b/libavcodec/v4l2_m2m_dec.c
index aa2d759e1e..cfeee7f2fb 100644
--- a/libavcodec/v4l2_m2m_dec.c
+++ b/libavcodec/v4l2_m2m_dec.c
@@ -23,12 +23,17 @@
#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 "codec_internal.h"
#include "libavcodec/decode.h"
+#include "libavcodec/internal.h"
+#include "libavcodec/hwconfig.h"
#include "v4l2_context.h"
#include "v4l2_m2m.h"
@@ -205,7 +210,44 @@ 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.
+ */
+ {
+ const enum AVPixelFormat *pix_fmts = NULL;
+ int num_pix_fmts = 0;
+ ret = avcodec_get_supported_config(avctx, NULL, AV_CODEC_CONFIG_PIX_FORMAT,
+ 0, (const void **) &pix_fmts,
&num_pix_fmts);
I don’t think here is the meant use case for avcodec_get_supported_config.
Specify available pixel format directly in pix_fmts.
+ if (ret < 0)
+ return ret;
+ if (pix_fmts == NULL || num_pix_fmts < 1)
+ return -1;
There is no which error code to use issue after remove
avcodec_get_supported_config.
AVCodec::pix_fmts was deprecated, so I replaced it with
avcodec_get_supported_config() in
https://github.com/ulmus-scott/FFmpeg/commit/7ac4b4fc2282b4fdda78ffb1a446ceb85b681661
Was that incorrect?
+ switch (ff_get_format(avctx, pix_fmts)) {
+ case AV_PIX_FMT_DRM_PRIME:
+ s->output_drm = 1;
+ break;
+ case AV_PIX_FMT_NONE:
+ return 0;
+ break;
Why return 0 for AV_PIX_FMT_NONE? It’s suspicious.
‘break’ can be removed.
That is from
https://github.com/lrusak/FFmpeg/commit/8405b573e83838e6b2fea99825fbef32ee9f7767
I agree return 0 is strange. All I can say is that is what the code
used by MythTV is and has been for years. (Maybe MythTV always requests
AV_PIX_FMT_DRM_PRIME?)
This change is not used by MythTV but maybe
https://github.com/lrusak/FFmpeg/commit/ffc4419f456c00ab71cf93f792b0473c6de14e64
is related or an alternate way of requesting the pixel format?
+ default:
+ break;
+ }
+ }
+
+ s->device_ref = av_hwdevice_ctx_alloc(AV_HWDEVICE_TYPE_DRM);
+ if (!s->device_ref) {
+ ret = AVERROR(ENOMEM);
+ return ret;
+ }
I’m not sure whether there is use case to let user specify device?
This is from
https://github.com/lrusak/FFmpeg/commit/b2c1f1eb39b54bf034497a7f2a7f23855d0a7cde
I don't know what you mean by "let user specify device".
+
s->avctx = avctx;
+ ret = av_hwdevice_ctx_init(s->device_ref);
+ if (ret < 0)
+ return ret;
+
ret = ff_v4l2_m2m_codec_init(priv);
if (ret) {
av_log(avctx, AV_LOG_ERROR, "can't configure decoder\n");
@@ -220,6 +262,16 @@ static av_cold int v4l2_decode_close(AVCodecContext *avctx)
return ff_v4l2_m2m_codec_end(avctx->priv_data);
}
+static void v4l2_flush(AVCodecContext *avctx)
+{
+ V4L2m2mPriv *priv = avctx->priv_data;
+ V4L2m2mContext* s = priv->context;
+
+ /* wait for pending buffer references */
+ if (atomic_load(&s->refcount))
+ while(sem_wait(&s->refsync) == -1 && errno == EINTR);
+}
Does refcount depends on users behavior like holding a frame? Is it possible to
run into deadlock here, e.g.,
user request flush while holding some frames?
I don't know, but Lukas Rusak removed that in his v5 patch (not used by
MythTV)
https://github.com/lrusak/FFmpeg/commit/8595d06d4909bbec0aa14625fcfc869c6bcef696
Original v4 patch for reference:
https://github.com/lrusak/FFmpeg/commit/e793ef82727d6d6f55c40844463d476e7e84efad
+
#define OFFSET(x) offsetof(V4L2m2mPriv, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_DECODING_PARAM
@@ -230,6 +282,11 @@ static const AVOption options[] = {
{ NULL},
};
+static const AVCodecHWConfigInternal *v4l2_m2m_hw_configs[] = {
+ HW_CONFIG_INTERNAL(DRM_PRIME),
Depends on whether allow user to specify drm device.
This is from the main patch
https://github.com/lrusak/FFmpeg/commit/2cb8052ac65a56d8a3f347a1e6f12d4449a5a614
Unless this is used internally by FFmpeg, MythTV does not appear to use it.
Regards,
Scott Theisen
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