[FFmpeg-cvslog] avcodec/alsdec: Fix decoding error with mono audio files

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Fri May  7 10:02:01 2021 +0900| [f7987ce966aaad841d584988e00454c685bff36f] | committer: Michael Niedermayer

avcodec/alsdec: Fix decoding error with mono audio files

highest_decoded_channel is modified to serve as meant.

Reported-by: Noboru Harada <noboru at ieee.org>

Regression since: a11aa5f3ed7ee4d2385a7b725d43f6070d790b4c
Fixes: Sin48k16bit1ch.mp4
Reviewed-by: Thilo Borgmann <thilo.borgmann at mail.de>
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=f7987ce966aaad841d584988e00454c685bff36f
---

 libavcodec/alsdec.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
index 0aada77450..ba873ec53a 100644
--- a/libavcodec/alsdec.c
+++ b/libavcodec/alsdec.c
@@ -1632,7 +1632,7 @@ static int read_frame_data(ALSDecContext *ctx, unsigned int ra_frame)
     AVCodecContext *avctx    = ctx->avctx;
     GetBitContext *gb = &ctx->gb;
     unsigned int div_blocks[32];                ///< block sizes.
-    unsigned int c;
+    int c;
     unsigned int js_blocks[2];
     uint32_t bs_info = 0;
     int ret;
@@ -1810,14 +1810,17 @@ static int decode_frame(AVCodecContext *avctx, void *data, int *got_frame_ptr,
     else
         ctx->cur_frame_length = sconf->frame_length;
 
-    ctx->highest_decoded_channel = 0;
+    ctx->highest_decoded_channel = -1;
     // decode the frame data
     if ((invalid_frame = read_frame_data(ctx, ra_frame)) < 0)
         av_log(ctx->avctx, AV_LOG_WARNING,
                "Reading frame data failed. Skipping RA unit.\n");
 
-    if (ctx->highest_decoded_channel == 0)
+    if (ctx->highest_decoded_channel == -1) {
+        av_log(ctx->avctx, AV_LOG_WARNING,
+               "No channel data decoded.\n");
         return AVERROR_INVALIDDATA;
+    }
 
     ctx->frame_id++;