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[FFmpeg-devel,v2] avcodec/aacenc: add strict bit rate control option

Message ID 20230425060952.2341011-1-jrwu@chromium.org
State Accepted
Commit b92af7b64e7acd015aea3ae1da2228c5a7e677bf
Headers show
Series [FFmpeg-devel,v2] avcodec/aacenc: add strict bit rate control option | expand

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Commit Message

Jeremy Wu April 25, 2023, 6:09 a.m. UTC 
From: Jeremy Wu <jrwu@google.com>

In certain use cases, controlling the maximum frame size is critical. An
example is when transmitting AAC packets over Bluetooth A2DP.

While the spec allows the packets to be fragmented (but UNRECOMMENDED),
in practice most headsets do not recognize nor reassemble such packets.

In this patch, we allow setting `bit_rate_tolerance` to 0 to indicate
that the specified bit rate should be treated as an upper bound up to
frame level.

Signed-off-by: Jeremy Wu <jrwu@chromium.org>
---
 libavcodec/aacenc.c        | 12 ++++++++++++
 libavcodec/options_table.h |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

Comments

Jeremy Wu May 19, 2023, 4:04 a.m. UTC | #1 
Friendly ping for review, thanks!
Lynne June 4, 2023, 1:42 a.m. UTC | #2 
May 19, 2023, 06:05 by jrwu@chromium.org:

> Friendly ping for review, thanks!
>

Patch applied, sorry for the delay.
Had my open tab for the patch buried very deep.
diff mbox series

Patch

diff --git a/libavcodec/aacenc.c b/libavcodec/aacenc.c
index ed036209e9..f48f057022 100644
--- a/libavcodec/aacenc.c
+++ b/libavcodec/aacenc.c
@@ -1106,6 +1106,18 @@  static int aac_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
         too_many_bits = FFMIN(too_many_bits, 6144 * s->channels - 3);
         too_few_bits = FFMIN(FFMAX(rate_bits - rate_bits/4, target_bits), too_many_bits);
 
+        /* When strict bit-rate control is demanded */
+        if (avctx->bit_rate_tolerance == 0) {
+            if (rate_bits < frame_bits) {
+                float ratio = ((float)rate_bits) / frame_bits;
+                s->lambda *= FFMIN(0.9f, ratio);
+                continue;
+            }
+            /* reset lambda when solution is found */
+            s->lambda = avctx->global_quality > 0 ? avctx->global_quality : 120;
+            break;
+        }
+
         /* When using ABR, be strict (but only for increasing) */
         too_few_bits = too_few_bits - too_few_bits/8;
         too_many_bits = too_many_bits + too_many_bits/2;
diff --git a/libavcodec/options_table.h b/libavcodec/options_table.h
index f331ce2861..716787aa59 100644
--- a/libavcodec/options_table.h
+++ b/libavcodec/options_table.h
@@ -50,7 +50,7 @@  static const AVOption avcodec_options[] = {
 {"bt", "Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far "
        "ratecontrol is willing to deviate from the target average bitrate value. This is not related "
        "to minimum/maximum bitrate. Lowering tolerance too much has an adverse effect on quality.",
-       OFFSET(bit_rate_tolerance), AV_OPT_TYPE_INT, {.i64 = AV_CODEC_DEFAULT_BITRATE*20 }, 1, INT_MAX, V|E},
+       OFFSET(bit_rate_tolerance), AV_OPT_TYPE_INT, {.i64 = AV_CODEC_DEFAULT_BITRATE*20 }, 0, INT_MAX, A|V|E},
 {"flags", NULL, OFFSET(flags), AV_OPT_TYPE_FLAGS, {.i64 = DEFAULT }, 0, UINT_MAX, V|A|S|E|D, "flags"},
 {"unaligned", "allow decoders to produce unaligned output", 0, AV_OPT_TYPE_CONST, { .i64 = AV_CODEC_FLAG_UNALIGNED }, INT_MIN, INT_MAX, V | D, "flags" },
 {"mv4", "use four motion vectors per macroblock (MPEG-4)", 0, AV_OPT_TYPE_CONST, {.i64 = AV_CODEC_FLAG_4MV }, INT_MIN, INT_MAX, V|E, "flags"},