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

Martin Storsjö git at videolan.org
Tue Jun 10 00:38:47 CEST 2014

ffmpeg | branch: release/1.2 | Martin Storsjö <martin at martin.st> | Fri Jun  6 12:03:09 2014 +0300| [401b3dafd989b4a016064e1906086be5ff3ea39a] | committer: Carl Eugen Hoyos

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.

Fixes part of Ticket3701

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
(cherry picked from commit fa8f060b75bf9074792a0f9ff4ed002652ef62b8)


> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=401b3dafd989b4a016064e1906086be5ff3ea39a

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

diff --git a/libavcodec/adpcmenc.c b/libavcodec/adpcmenc.c
index fed0cc8..5bcaeb1 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;

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