[FFmpeg-devel] [PATCH] avcodec/alac: fix decode errors on empty last frames (PR #21111)

[rmmh via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21111 opened by rmmh
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21111
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21111.patch

iOS Voice Memos frequently produces ALAC files with a zero-sample last
frame. Instead of bubbling up an error that might cause a transcode to
fail, simply don't decode the frame.


>From f2a31efae7c42aa8bac2a4747df0fcad40a62868 Mon Sep 17 00:00:00 2001
From: Ryan Hitchman <hitchmanr@gmail.com>
Date: Fri, 5 Dec 2025 09:20:29 -0700
Subject: [PATCH] avcodec/alac: fix decode errors on empty last frames

iOS Voice Memos frequently produces ALAC files with a zero-sample last
frame. Instead of bubbling up an error that might cause a transcode to
fail, simply don't decode the frame.
---
 libavcodec/alac.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libavcodec/alac.c b/libavcodec/alac.c
index f91288e97c..0acc568174 100644
--- a/libavcodec/alac.c
+++ b/libavcodec/alac.c
@@ -267,7 +267,9 @@ static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
         output_samples = get_bits_long(gb, 32);
     else
         output_samples = alac->max_samples_per_frame;
-    if (!output_samples || output_samples > alac->max_samples_per_frame) {
+    if (!output_samples) 
+        return 0;
+    if (output_samples > alac->max_samples_per_frame) {
         av_log(avctx, AV_LOG_ERROR, "invalid samples per frame: %"PRIu32"\n",
                output_samples);
         return AVERROR_INVALIDDATA;
-- 
2.49.1

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