This is an option to modify the behaviour of the writer, not a syntax
field.
---
Tested by hacking av1_metadata. For example, adding:
av_opt_set_int(ctx->common.output->priv_data, "fixed_obu_size_length", 7, 0);
gets you OBU headers that look like:
[trace_headers @ 0x55706fcb2880] OBU header
[trace_headers @ 0x55706fcb2880] 0 obu_forbidden_bit
0 = 0
[trace_headers @ 0x55706fcb2880] 1 obu_type
0100 = 4
[trace_headers @ 0x55706fcb2880] 5 obu_extension_flag
0 = 0
[trace_headers @ 0x55706fcb2880] 6 obu_has_size_field
1 = 1
[trace_headers @ 0x55706fcb2880] 7 obu_reserved_1bit
0 = 0
[trace_headers @ 0x55706fcb2880] 8 obu_size
10101110100010101000000010000000100000001000000000000000 = 1326
It's not obvious that there is any value in exposing this option more
generally, though? It could made a visible option of av1_metadata or others if
there is any use-case for it.
Thanks,
- Mark
libavcodec/cbs_av1.c | 31 +++++++++++++++++++++----------
libavcodec/cbs_av1.h | 5 ++++-
libavcodec/vaapi_encode_av1.c | 4 +++-
3 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
index 4e687ace79..ed9a7b80d4 100644
--- a/libavcodec/cbs_av1.c
+++ b/libavcodec/cbs_av1.c
@@ -138,19 +138,25 @@ static int cbs_av1_read_leb128(CodedBitstreamContext
*ctx, GetBitContext *gbc,
return 0;
}
-/** Minimum byte length will be used to indicate the len128 of value if
byte_len is 0. */
static int cbs_av1_write_leb128(CodedBitstreamContext *ctx, PutBitContext *pbc,
- const char *name, uint64_t value, uint8_t
byte_len)
+ const char *name, uint64_t value, int
fixed_length)
{
int len, i;
uint8_t byte;
CBS_TRACE_WRITE_START();
- if (byte_len)
- av_assert0(byte_len >= (av_log2(value) + 7) / 7);
+ len = (av_log2(value) + 7) / 7;
- len = byte_len ? byte_len : (av_log2(value) + 7) / 7;
+ if (fixed_length) {
+ if (fixed_length < len) {
+ av_log(ctx->log_ctx, AV_LOG_ERROR, "OBU is too large for "
+ "fixed length size field (%d > %d).\n",
+ len, fixed_length);
+ return AVERROR(EINVAL);
+ }
+ len = fixed_length;
+ }
for (i = 0; i < len; i++) {
if (put_bits_left(pbc) < 8)
@@ -1006,8 +1012,8 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
if (obu->header.obu_has_size_field) {
pbc_tmp = *pbc;
- if (obu->obu_size_byte_len) {
- for (int i = 0; i < obu->obu_size_byte_len; i++)
+ if (priv->fixed_obu_size_length) {
+ for (int i = 0; i < priv->fixed_obu_size_length; i++)
put_bits(pbc, 8, 0);
} else {
// Add space for the size field to fill later.
@@ -1133,7 +1139,8 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
end_pos /= 8;
*pbc = pbc_tmp;
- err = cbs_av1_write_leb128(ctx, pbc, "obu_size", obu->obu_size,
obu->obu_size_byte_len);
+ err = cbs_av1_write_leb128(ctx, pbc, "obu_size", obu->obu_size,
+ priv->fixed_obu_size_length);
if (err < 0)
goto error;
@@ -1150,10 +1157,12 @@ static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
}
if (obu->obu_size > 0) {
- if (!obu->obu_size_byte_len) {
- obu->obu_size_byte_len = start_pos - data_pos;
+ if (!priv->fixed_obu_size_length) {
memmove(pbc->buf + data_pos,
pbc->buf + start_pos, header_size);
+ } else {
+ // The size was fixed so the following data was
+ // already written in the correct place.
}
skip_put_bytes(pbc, header_size);
@@ -1273,6 +1282,8 @@ static const CodedBitstreamUnitTypeDescriptor
cbs_av1_unit_types[] = {
static const AVOption cbs_av1_options[] = {
{ "operating_point", "Set operating point to select layers to parse from a
scalable bitstream",
OFFSET(operating_point), AV_OPT_TYPE_INT, { .i64 =
-1 }, -1, AV1_MAX_OPERATING_POINTS - 1, 0 },
+ { "fixed_obu_size_length", "Set fixed length of the obu_size field",
+ OFFSET(fixed_obu_size_length), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 8, 0 },
{ NULL }
};
diff --git a/libavcodec/cbs_av1.h b/libavcodec/cbs_av1.h
index a9e2d2284f..7924257164 100644
--- a/libavcodec/cbs_av1.h
+++ b/libavcodec/cbs_av1.h
@@ -401,7 +401,6 @@ typedef struct AV1RawOBU {
AV1RawOBUHeader header;
size_t obu_size;
- uint8_t obu_size_byte_len;
union {
AV1RawSequenceHeader sequence_header;
@@ -468,6 +467,10 @@ typedef struct CodedBitstreamAV1Context {
// AVOptions
int operating_point;
+ // When writing, fix the length in bytes of the obu_size field.
+ // Writing will fail with an error if an OBU larger than can be
+ // represented by the fixed size is encountered.
+ int fixed_obu_size_length;
} CodedBitstreamAV1Context;
diff --git a/libavcodec/vaapi_encode_av1.c b/libavcodec/vaapi_encode_av1.c
index 3ff1c47b53..861bf4a13b 100644
--- a/libavcodec/vaapi_encode_av1.c
+++ b/libavcodec/vaapi_encode_av1.c
@@ -133,6 +133,9 @@ static av_cold int
vaapi_encode_av1_configure(AVCodecContext *avctx)
priv->cbc->trace_context = ctx;
priv->cbc->trace_write_callback = vaapi_encode_av1_trace_write_log;
+ av_opt_set_int(priv->cbc->priv_data, "fixed_obu_size_length",
+ priv->attr_ext2.bits.obu_size_bytes_minus1 + 1, 0);
+
if (ctx->rc_mode->quality) {
priv->q_idx_p = av_clip(ctx->rc_quality, 0, AV1_MAX_QUANT);
if (fabs(avctx->i_quant_factor) > 0.0)
@@ -634,7 +637,6 @@ static int
vaapi_encode_av1_init_picture_params(AVCodecContext *avctx,
}
}
- fh_obu->obu_size_byte_len = priv->attr_ext2.bits.obu_size_bytes_minus1 + 1;
ret = vaapi_encode_av1_add_obu(avctx, obu, AV1_OBU_FRAME_HEADER,
&priv->fh);
if (ret < 0)
goto end;
--
2.39.2
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