[PR] avformat/wavdec: cache avio_size() before footer seeks (PR #24123)

PR #24123 opened by adorn
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24123
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/24123.patch

Over HTTP, seeking to a trailing chunk can make avio_size() stale, so the PCM
duration guard fails and duration is N/A. Cache size before seeking.

Fixes #24122



>From 1e46f021bd389b83b6081fd95d92f1f170292d8a Mon Sep 17 00:00:00 2001
From: Andreas Menze <[email protected]>
Date: Thu, 13 Aug 2026 09:11:27 +0200
Subject: [PATCH] avformat/wavdec: cache avio_size() before footer seeks

Over HTTP, seeking to a trailing chunk can make avio_size() stale, so the PCM
duration guard fails and duration is N/A. Cache size before seeking.

Fixes #24122
---
 libavformat/wavdec.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libavformat/wavdec.c b/libavformat/wavdec.c
index 8501d94deb..8d19e52ead 100644
--- a/libavformat/wavdec.c
+++ b/libavformat/wavdec.c
@@ -370,11 +370,13 @@ static int wav_read_header(AVFormatContext *s)
     WAVDemuxContext *wav = s->priv_data;
     int ret, got_fmt = 0, got_xma2 = 0;
     int64_t next_tag_ofs, data_ofs = -1;
+    int64_t filesize;
 
     wav->unaligned = avio_tell(s->pb) & 1;
 
     wav->smv_data_ofs = -1;
 
+    filesize = avio_size(pb);
     /* read chunk ID */
     tag = avio_rl32(pb);
     switch (tag) {
@@ -661,7 +663,7 @@ break_loop:
         if (   st->codecpar->ch_layout.nb_channels
             && data_size
             && av_get_bits_per_sample(st->codecpar->codec_id)
-            && wav->data_end <= avio_size(pb))
+            && wav->data_end <= filesize)
             sample_count = (data_size << 3)
                                   /
                 (st->codecpar->ch_layout.nb_channels * (uint64_t)av_get_bits_per_sample(st->codecpar->codec_id));
-- 
2.52.0

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