[FFmpeg-cvslog] adpcm: Write the proper predictor in trellis mode in IMA QT

[Martin Storsjö]

ffmpeg | branch: release/1.1 | Martin Storsjö <martin at martin.st> | Thu Jun  5 14:49:14 2014 +0300| [21d3e0ac9e1719d8444b3f5466983587ac0ad240] | committer: Luca Barbato

adpcm: Write the proper predictor in trellis mode in IMA QT

The actual predictor value, set by the trellis code, never
was written back into the variable that was written into
the block header. This was accidentally removed in b304244b.

This significantly improves the audio quality of the trellis
case, which was plain broken since b304244b.

Encoding IMA QT with trellis still actually gives a slightly
worse quality than without trellis, since the trellis encoder
doesn't use the exact same way of rounding as in
adpcm_ima_qt_compress_sample and adpcm_ima_qt_expand_nibble.

CC: libav-stable at libav.org
Signed-off-by: Martin Storsjö <martin at martin.st>
(cherry picked from commit 0776e0ef6ba4160281ef3fabea43e670f3792b4a)
Signed-off-by: Luca Barbato <lu_zero at gentoo.org>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=21d3e0ac9e1719d8444b3f5466983587ac0ad240
---

 libavcodec/adpcmenc.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/libavcodec/adpcmenc.c b/libavcodec/adpcmenc.c
index 116458b..aa88395 100644
--- a/libavcodec/adpcmenc.c
+++ b/libavcodec/adpcmenc.c
@@ -561,6 +561,7 @@ static int adpcm_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
                                        64, 1);
                 for (i = 0; i < 64; i++)
                     put_bits(&pb, 4, buf[i ^ 1]);
+                status->prev_sample = status->predictor;
             } else {
                 for (i = 0; i < 64; i += 2) {
                     int t1, t2;