[FFmpeg-cvslog] avcodec/ac3enc: Use actual size of buffer in init_put_bits()

[Andreas Rheinhardt]

ffmpeg | branch: release/4.4 | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Mon Mar 29 18:19:43 2021 +0200| [ffb599458f34c9ba674dc82e8f3ba07ef3b01948] | committer: Andreas Rheinhardt

avcodec/ac3enc: Use actual size of buffer in init_put_bits()

Since the very beginning (since de6d9b6404bfd1c589799142da5a95428f146edd)
the AC-3 encoder used AC3_MAX_CODED_FRAME_SIZE (namely 3840) for the
size of the output buffer (without any check at all).
This causes problems when encoding EAC-3 for which the maximum is too small,
smaller than the actual size of the buffer: One can run into asserts used
by the PutBits API. Ticket #8513 is about such a case and this commit
fixes it by using the real size of the buffer.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
(cherry picked from commit 968c158abde36ebb7520706a69eebe3e8eacbd81)

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ffb599458f34c9ba674dc82e8f3ba07ef3b01948
---

 libavcodec/ac3.h    | 1 -
 libavcodec/ac3enc.c | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)

diff --git a/libavcodec/ac3.h b/libavcodec/ac3.h
index f8f6a81f45..e358f8d9e3 100644
--- a/libavcodec/ac3.h
+++ b/libavcodec/ac3.h
@@ -27,7 +27,6 @@
 #ifndef AVCODEC_AC3_H
 #define AVCODEC_AC3_H
 
-#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
 #define EAC3_MAX_CHANNELS 16          /**< maximum number of channels in EAC3 */
 #define AC3_MAX_CHANNELS 7            /**< maximum number of channels, including coupling channel */
 #define CPL_CH 0                      /**< coupling channel index */
diff --git a/libavcodec/ac3enc.c b/libavcodec/ac3enc.c
index 8044e6dcd0..4cfd0afe12 100644
--- a/libavcodec/ac3enc.c
+++ b/libavcodec/ac3enc.c
@@ -1729,7 +1729,7 @@ static void ac3_output_frame(AC3EncodeContext *s, unsigned char *frame)
 {
     int blk;
 
-    init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
+    init_put_bits(&s->pb, frame, s->frame_size);
 
     s->output_frame_header(s);