[FFmpeg-cvslog] aacdec_usac: skip coeff decoding if the number to be decoded is 0

[Lynne]

ffmpeg | branch: master | Lynne <dev at lynne.ee> | Thu Jun  6 04:38:47 2024 +0200| [a18d0659f403cf4b93a3c5a293a42e0ff7348e90] | committer: Lynne

aacdec_usac: skip coeff decoding if the number to be decoded is 0

Yet another thing not mentioned in the spec.

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=a18d0659f403cf4b93a3c5a293a42e0ff7348e90
---

 libavcodec/aac/aacdec_usac.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libavcodec/aac/aacdec_usac.c b/libavcodec/aac/aacdec_usac.c
index 97655787ee..5dd489a43b 100644
--- a/libavcodec/aac/aacdec_usac.c
+++ b/libavcodec/aac/aacdec_usac.c
@@ -572,9 +572,15 @@ static int decode_spectrum_and_dequant_ac(AACDecContext *s, float coef[1024],
     int gb_count;
     GetBitContext gb2;
 
-    ff_aac_ac_init(&ac, gb);
     c = ff_aac_ac_map_process(state, reset, N);
 
+    if (!len) {
+        ff_aac_ac_finish(state, 0, N);
+        return 0;
+    }
+
+    ff_aac_ac_init(&ac, gb);
+
     /* Backup reader for rolling back by 14 bits at the end */
     gb2 = *gb;
     gb_count = get_bits_count(&gb2);