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Leverage sws_is_noop for video reformat shortcuts #2327

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Merged
WyattBlue merged 1 commit into from
Jun 24, 2026
+34 −61
Merged

Leverage sws_is_noop for video reformat shortcuts #2327

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2 changes: 1 addition & 1 deletion av/video/reformatter.pxd
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ cdef extern from "libswscale/swscale.h" nogil:

cdef SwsContext *sws_alloc_context()
cdef void sws_free_context(SwsContext **ctx)
cdef int sws_is_noop(const lib.AVFrame *dst, const lib.AVFrame *src)
cdef int sws_scale_frame(SwsContext *c, lib.AVFrame *dst, const lib.AVFrame *src)

cdef class VideoReformatter:
Expand All @@ -45,5 +46,4 @@ cdef class VideoReformatter:
int dst_colorspace, int interpolation,
int src_color_range, int dst_color_range,
int dst_color_trc, int dst_color_primaries,
bint set_dst_color_trc, bint set_dst_color_primaries,
int threads)
93 changes: 33 additions & 60 deletions av/video/reformatter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -220,18 +220,16 @@ def reformat(
)
c_src_color_range = _resolve_enum_value(src_color_range, ColorRange, 0)
c_dst_color_range = _resolve_enum_value(dst_color_range, ColorRange, 0)
c_dst_color_trc = _resolve_enum_value(dst_color_trc, ColorTrc, 0)
c_dst_color_trc = _resolve_enum_value(
dst_color_trc, ColorTrc, frame.ptr.color_trc
)
c_dst_color_primaries = _resolve_enum_value(
dst_color_primaries, ColorPrimaries, 0
dst_color_primaries, ColorPrimaries, frame.ptr.color_primaries
)
c_threads: cython.int = threads if threads is not None else 0
c_width: cython.int = width if width is not None else frame.ptr.width
c_height: cython.int = height if height is not None else frame.ptr.height

# Track whether user explicitly specified destination metadata
set_dst_color_trc: cython.bint = dst_color_trc is not None
set_dst_color_primaries: cython.bint = dst_color_primaries is not None

return self._reformat(
frame,
c_width,
Expand All @@ -244,8 +242,6 @@ def reformat(
c_dst_color_range,
c_dst_color_trc,
c_dst_color_primaries,
set_dst_color_trc,
set_dst_color_primaries,
c_threads,
)

Expand All @@ -263,46 +259,41 @@ def _reformat(
dst_color_range: cython.int,
dst_color_trc: cython.int,
dst_color_primaries: cython.int,
set_dst_color_trc: cython.bint,
set_dst_color_primaries: cython.bint,
threads: cython.int,
):
if frame.ptr.format < 0:
raise ValueError("Frame does not have format set.")

src_format = cython.cast(lib.AVPixelFormat, frame.ptr.format)

# Shortcut!
if (
dst_format == src_format
and width == frame.ptr.width
and height == frame.ptr.height
and dst_colorspace == src_colorspace
and src_color_range == dst_color_range
and not set_dst_color_trc
and not set_dst_color_primaries
):
return frame

if frame.ptr.hw_frames_ctx:
frame_sw = alloc_video_frame()
err_check(lib.av_hwframe_transfer_data(frame_sw.ptr, frame.ptr, 0))
frame_sw._copy_internal_attributes(frame, data_layout=False)
frame_sw._init_user_attributes()
frame = frame_sw
src_format = cython.cast(lib.AVPixelFormat, frame.ptr.format)

# Check for shortcut again, in case dst_format matches the downloaded frame's sw_format
if (
dst_format == src_format
and width == frame.ptr.width
and height == frame.ptr.height
and dst_colorspace == src_colorspace
and src_color_range == dst_color_range
and not set_dst_color_trc
and not set_dst_color_primaries
):
frame._init_user_attributes()
return frame

new_frame: VideoFrame = alloc_video_frame()
new_frame._copy_internal_attributes(frame, data_layout=False)
new_frame.ptr.format = dst_format
new_frame.ptr.width = width
new_frame.ptr.height = height
new_frame.ptr.color_trc = cython.cast(
lib.AVColorTransferCharacteristic, dst_color_trc
)
new_frame.ptr.color_primaries = cython.cast(
lib.AVColorPrimaries, dst_color_primaries
)

# Translate source and destination colorspace/range from SWS_CS_* to AVCOL_*
# so sws_is_noop and sws_scale_frame understand them
frame_src_colorspace: lib.AVColorSpace = frame.ptr.colorspace
frame_src_color_range: lib.AVColorRange = frame.ptr.color_range
_set_frame_colorspace(frame.ptr, src_colorspace, src_color_range)
_set_frame_colorspace(new_frame.ptr, dst_colorspace, dst_color_range)

# Shortcut if sws_scale_frame would be a no-op
is_noop: cython.bint = sws_is_noop(new_frame.ptr, frame.ptr) != 0
if is_noop:
# Restore source frame colorspace/range to avoid side effects
frame.ptr.colorspace = frame_src_colorspace
frame.ptr.color_range = frame_src_color_range
return frame

if self.ptr == cython.NULL:
self.ptr = sws_alloc_context()
Expand All @@ -311,16 +302,8 @@ def _reformat(
self.ptr.threads = threads
self.ptr.flags = cython.cast(cython.uint, interpolation)

new_frame: VideoFrame = alloc_video_frame()
new_frame._copy_internal_attributes(frame)
# Allocate frame buffers and perform the conversion
new_frame._init(dst_format, width, height)

# Set source frame colorspace/range so sws_scale_frame can read it
frame_src_colorspace: lib.AVColorSpace = frame.ptr.colorspace
frame_src_color_range: lib.AVColorRange = frame.ptr.color_range
_set_frame_colorspace(frame.ptr, src_colorspace, src_color_range)
_set_frame_colorspace(new_frame.ptr, dst_colorspace, dst_color_range)

with cython.nogil:
ret = sws_scale_frame(self.ptr, new_frame.ptr, frame.ptr)

Expand All @@ -330,14 +313,4 @@ def _reformat(

err_check(ret)

# Set metadata-only properties on the output frame if explicitly specified
if set_dst_color_trc:
new_frame.ptr.color_trc = cython.cast(
lib.AVColorTransferCharacteristic, dst_color_trc
)
if set_dst_color_primaries:
new_frame.ptr.color_primaries = cython.cast(
lib.AVColorPrimaries, dst_color_primaries
)

return new_frame
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