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Subject[PATCH v4 1/6] media: uapi: h264: Add DPB entry field reference flags
From: Jonas Karlman <>

Using the field information attached to v4l2 buffers is not enough to
determine the type of field referenced by a DPB entry: the decoded
frame might contain the full picture (both top and bottom fields)
but the reference only point to one of them.
Let's add new V4L2_H264_DPB_ENTRY_FLAG_ flags to express that.

Signed-off-by: Jonas Karlman <>
[Keep only 2 flags and add some details about they mean]
Signed-off-by: Boris Brezillon <>
Signed-off-by: Ezequiel Garcia <>
* None
* This patch was previously part of
* Kept the FIELD and BOTTOM_FIELD flags
* Updated the doc with more details
Documentation/media/uapi/v4l/ext-ctrls-codec.rst | 16 ++++++++++++++++
include/media/h264-ctrls.h | 2 ++
2 files changed, 18 insertions(+)

diff --git a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
index 28313c0f4e7c..d4fc5f25aa14 100644
--- a/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
+++ b/Documentation/media/uapi/v4l/ext-ctrls-codec.rst
@@ -2028,6 +2028,22 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
- 0x00000004
- The DPB entry is a long term reference frame
+ * - ``V4L2_H264_DPB_ENTRY_FLAG_FIELD``
+ - 0x00000008
+ - The DPB entry is a field reference, which means only one of the field
+ will be used when decoding the new frame/field. When not set the DPB
+ entry is a frame reference (both fields will be used). Note that this
+ flag does not say anything about the number of fields contained in the
+ reference frame, it just describes the one used to decode the new
+ field/frame
+ - 0x00000010
+ - The DPB entry is a bottom field reference (only the bottom field of the
+ reference frame is needed to decode the new frame/field). Only valid if
+ V4L2_H264_DPB_ENTRY_FLAG_FIELD is set. When
+ V4L2_H264_DPB_ENTRY_FLAG_FIELD is set but
+ V4L2_H264_DPB_ENTRY_FLAG_BOTTOM_FIELD is not, that means the
+ DPB entry is a top field reference

Specifies the decoding mode to use. Currently exposes slice-based and
diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
index e877bf1d537c..1c6ff7d63bca 100644
--- a/include/media/h264-ctrls.h
+++ b/include/media/h264-ctrls.h
@@ -185,6 +185,8 @@ struct v4l2_ctrl_h264_slice_params {
#define V4L2_H264_DPB_ENTRY_FLAG_VALID 0x01
#define V4L2_H264_DPB_ENTRY_FLAG_ACTIVE 0x02
#define V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM 0x04
+#define V4L2_H264_DPB_ENTRY_FLAG_FIELD 0x08

struct v4l2_h264_dpb_entry {
__u64 reference_ts;
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