From 93d65e3d92623500b69fe7ccba43f6b6266c3250 Mon Sep 17 00:00:00 2001
From: Justin Ruggles <justin.ruggles@gmail.com>
Date: Sat, 31 Jul 2010 16:37:23 +0000
Subject: [PATCH] Estimate frame size during encoding.

Originally committed as revision 24619 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/flacenc.c | 54 +++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 3 deletions(-)

diff --git a/libavcodec/flacenc.c b/libavcodec/flacenc.c
index 57c0a65726..7eabd9c994 100644
--- a/libavcodec/flacenc.c
+++ b/libavcodec/flacenc.c
@@ -791,7 +791,7 @@ static void encode_residual_lpc(int32_t *res, const int32_t *smp, int n,
 }
 
 
-static int encode_residual(FlacEncodeContext *s, int ch)
+static int encode_residual_ch(FlacEncodeContext *s, int ch)
 {
     int i, n;
     int min_order, max_order, opt_order, precision, omethod;
@@ -936,6 +936,55 @@ static int encode_residual(FlacEncodeContext *s, int ch)
 }
 
 
+static int count_frame_header(FlacEncodeContext *s)
+{
+    uint8_t tmp;
+    int count;
+
+    /*
+    <14> Sync code
+    <1>  Reserved
+    <1>  Blocking strategy
+    <4>  Block size in inter-channel samples
+    <4>  Sample rate
+    <4>  Channel assignment
+    <3>  Sample size in bits
+    <1>  Reserved
+    */
+    count = 32;
+
+    /* coded frame number */
+    PUT_UTF8(s->frame_count, tmp, count += 8;)
+
+    /* explicit block size */
+    count += FFMAX(0, s->frame.bs_code[0] - 5) * 8;
+
+    /* explicit sample rate */
+    count += ((s->sr_code[0] == 12) + (s->sr_code[0] > 12)) * 8;
+
+    /* frame header CRC-8 */
+    count += 8;
+
+    return count;
+}
+
+
+static int encode_frame(FlacEncodeContext *s)
+{
+    int ch, count;
+
+    count = count_frame_header(s);
+
+    for (ch = 0; ch < s->channels; ch++)
+        count += encode_residual_ch(s, ch);
+
+    count += (8 - (count & 7)) & 7; // byte alignment
+    count += 16;                    // CRC-16
+
+    return count >> 3;
+}
+
+
 static int encode_residual_v(FlacEncodeContext *s, int ch)
 {
     int i, n;
@@ -1214,8 +1263,7 @@ static int flac_encode_frame(AVCodecContext *avctx, uint8_t *frame,
 
     channel_decorrelation(s);
 
-    for (ch = 0; ch < s->channels; ch++)
-        encode_residual(s, ch);
+    encode_frame(s);
 
 write_frame:
     init_put_bits(&s->pb, frame, buf_size);