when writing a unit from content.
Writing a unit (i.e. assembling it from its decomposed form) currently
always uses an intermediate buffer; only after the unit has been
completely assembled in this buffer (so that, in particular, the needed
size is known), is the final buffer allocated and the data copied.
This works well for most types of units except one: The slice/frame
units that usually make up the bulk of the whole data. Only their
headers are reassembled from content. Their actual data are mostly just
copied into the write buffer. Given that the size of the actual data is
known, one has a very good estimate on the needed size after having
assembled the slice/frame header only. If one allocated the necessary
buffer now and directly copied the frame header and frame data into it,
one can avoid copying the data into the temporary buffer.
This commit lays the groundwork for doing so by moving the data buffer's
allocation into the (codec-dependent) write_unit function. It does not
avoid copying yet.
Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@gmail.com>
---
libavcodec/cbs.c | 38 ++++++++++++++++++++++----------------
libavcodec/cbs_av1.c | 2 +-
libavcodec/cbs_h2645.c | 4 ++--
libavcodec/cbs_internal.h | 12 +++++++++++-
libavcodec/cbs_jpeg.c | 10 ++++++++--
libavcodec/cbs_mpeg2.c | 10 ++++++++--
libavcodec/cbs_vp9.c | 2 +-
7 files changed, 53 insertions(+), 25 deletions(-)
diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c
index 0badb192d9..aa2e4904d0 100644
--- a/libavcodec/cbs.c
+++ b/libavcodec/cbs.c
@@ -283,6 +283,28 @@ int ff_cbs_read(CodedBitstreamContext *ctx,
return cbs_read_fragment_content(ctx, frag);
}
+int ff_cbs_default_write_unit_data(CodedBitstreamContext *ctx,
+ CodedBitstreamUnit *unit,
+ PutBitContext *pbc)
+{
+ int err;
+
+ if (put_bits_count(pbc) % 8)
+ unit->data_bit_padding = 8 - put_bits_count(pbc) % 8;
+ else
+ unit->data_bit_padding = 0;
+
+ flush_put_bits(pbc);
+
+ err = ff_cbs_alloc_unit_data(ctx, unit, put_bits_count(pbc) / 8);
+ if (err < 0)
+ return err;
+
+ memcpy(unit->data, pbc->buf, unit->data_size);
+
+ return 0;
+}
+
static int cbs_write_unit_data(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit)
{
@@ -318,22 +340,6 @@ static int cbs_write_unit_data(CodedBitstreamContext *ctx,
return ret;
}
- // Overflow but we didn't notice.
- av_assert0(put_bits_count(&pbc) <= 8 * ctx->write_buffer_size);
-
- if (put_bits_count(&pbc) % 8)
- unit->data_bit_padding = 8 - put_bits_count(&pbc) % 8;
- else
- unit->data_bit_padding = 0;
-
- flush_put_bits(&pbc);
-
- ret = ff_cbs_alloc_unit_data(ctx, unit, put_bits_count(&pbc) / 8);
- if (ret < 0)
- return ret;
-
- memcpy(unit->data, ctx->write_buffer, unit->data_size);
-
return 0;
}
diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
index bbe4461130..7ff5539fb8 100644
--- a/libavcodec/cbs_av1.c
+++ b/libavcodec/cbs_av1.c
@@ -1217,7 +1217,7 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
// OBU data must be byte-aligned.
av_assert0(put_bits_count(pbc) % 8 == 0);
- return 0;
+ return ff_cbs_default_write_unit_data(ctx, unit, pbc);
}
static int cbs_av1_assemble_fragment(CodedBitstreamContext *ctx,
diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
index 88fa0029cd..d3d5342bad 100644
--- a/libavcodec/cbs_h2645.c
+++ b/libavcodec/cbs_h2645.c
@@ -1265,7 +1265,7 @@ static int cbs_h264_write_nal_unit(CodedBitstreamContext
*ctx,
return AVERROR_PATCHWELCOME;
}
- return 0;
+ return ff_cbs_default_write_unit_data(ctx, unit, pbc);
}
static int cbs_h265_write_nal_unit(CodedBitstreamContext *ctx,
@@ -1377,7 +1377,7 @@ static int cbs_h265_write_nal_unit(CodedBitstreamContext
*ctx,
return AVERROR_PATCHWELCOME;
}
- return 0;
+ return ff_cbs_default_write_unit_data(ctx, unit, pbc);
}
static int cbs_h2645_assemble_fragment(CodedBitstreamContext *ctx,
diff --git a/libavcodec/cbs_internal.h b/libavcodec/cbs_internal.h
index 4c5a535ca6..96c2a1ac80 100644
--- a/libavcodec/cbs_internal.h
+++ b/libavcodec/cbs_internal.h
@@ -44,7 +44,9 @@ typedef struct CodedBitstreamType {
int (*read_unit)(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit);
- // Write the data bitstream from unit->content into pbc.
+ // Write the data bitstream from unit->content. This includes
+ // allocating the buffer as well as setting all of unit's data-fields.
+ // The supplied PutBitContext may be used as temporary buffer.
// Return value AVERROR(ENOSPC) indicates that pbc was too small.
int (*write_unit)(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
@@ -60,6 +62,14 @@ typedef struct CodedBitstreamType {
} CodedBitstreamType;
+// Helper function to convert pbc's content into a unit's data.
+// Allocates and copies data and sets all of unit's data-fields.
+
+int ff_cbs_default_write_unit_data(CodedBitstreamContext *ctx,
+ CodedBitstreamUnit *unit,
+ PutBitContext *pbc);
+
+
// Helper functions for trace output.
void ff_cbs_trace_header(CodedBitstreamContext *ctx,
diff --git a/libavcodec/cbs_jpeg.c b/libavcodec/cbs_jpeg.c
index 64fe70beab..da22bdf720 100644
--- a/libavcodec/cbs_jpeg.c
+++ b/libavcodec/cbs_jpeg.c
@@ -384,10 +384,16 @@ static int cbs_jpeg_write_unit(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
+ int err;
+
if (unit->type == JPEG_MARKER_SOS)
- return cbs_jpeg_write_scan (ctx, unit, pbc);
+ err = cbs_jpeg_write_scan (ctx, unit, pbc);
else
- return cbs_jpeg_write_segment(ctx, unit, pbc);
+ err = cbs_jpeg_write_segment(ctx, unit, pbc);
+ if (err < 0)
+ return err;
+
+ return ff_cbs_default_write_unit_data(ctx, unit, pbc);
}
static int cbs_jpeg_assemble_fragment(CodedBitstreamContext *ctx,
diff --git a/libavcodec/cbs_mpeg2.c b/libavcodec/cbs_mpeg2.c
index 13d871cc89..ba5e2417c2 100644
--- a/libavcodec/cbs_mpeg2.c
+++ b/libavcodec/cbs_mpeg2.c
@@ -374,10 +374,16 @@ static int cbs_mpeg2_write_unit(CodedBitstreamContext
*ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
+ int err;
+
if (MPEG2_START_IS_SLICE(unit->type))
- return cbs_mpeg2_write_slice (ctx, unit, pbc);
+ err = cbs_mpeg2_write_slice (ctx, unit, pbc);
else
- return cbs_mpeg2_write_header(ctx, unit, pbc);
+ err = cbs_mpeg2_write_header(ctx, unit, pbc);
+ if (err < 0)
+ return err;
+
+ return ff_cbs_default_write_unit_data(ctx, unit, pbc);
}
static int cbs_mpeg2_assemble_fragment(CodedBitstreamContext *ctx,
diff --git a/libavcodec/cbs_vp9.c b/libavcodec/cbs_vp9.c
index 42e4dcf5ac..a74c4f4cec 100644
--- a/libavcodec/cbs_vp9.c
+++ b/libavcodec/cbs_vp9.c
@@ -544,7 +544,7 @@ static int cbs_vp9_write_unit(CodedBitstreamContext *ctx,
skip_put_bytes(pbc, frame->data_size);
}
- return 0;
+ return ff_cbs_default_write_unit_data(ctx, unit, pbc);
}
static int cbs_vp9_assemble_fragment(CodedBitstreamContext *ctx,
--
2.20.1
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