[FFmpeg-devel] [PATCH] doc/examples/vaapi_encode: fix invalid check on fwrite (PR #20396)

[Zhao Zhili via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #20396 opened by Zhao Zhili (quink)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20396
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20396.patch

Firstly, the order of the parameters to fwrite was incorrect, which
make fwrite always return 1 or 0.

Secondly, enc_pkt->size is 0 after av_packet_unref, which makes
the check invalid again.

Fix regression from 3e4bfff2.

Co-Authored-by: Jin Bo <jinbo@loongson.cn>
Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>


>From 5147580520ad627ffbae692119c4e92a7c489c76 Mon Sep 17 00:00:00 2001
From: Zhao Zhili <zhilizhao@tencent.com>
Date: Tue, 2 Sep 2025 18:04:11 +0800
Subject: [PATCH] doc/examples/vaapi_encode: fix invalid check on fwrite

Firstly, the order of the parameters to fwrite was incorrect, which
make fwrite always return 1 or 0.

Secondly, enc_pkt->size is 0 after av_packet_unref, which makes
the check invalid again.

Fix regression from 3e4bfff2.

Co-Authored-by: Jin Bo <jinbo@loongson.cn>
Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
---
 doc/examples/vaapi_encode.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/doc/examples/vaapi_encode.c b/doc/examples/vaapi_encode.c
index ff3ebb1e2b..3d718c4c4f 100644
--- a/doc/examples/vaapi_encode.c
+++ b/doc/examples/vaapi_encode.c
@@ -86,9 +86,10 @@ static int encode_write(AVCodecContext *avctx, AVFrame *frame, FILE *fout)
             break;
 
         enc_pkt->stream_index = 0;
-        ret = fwrite(enc_pkt->data, enc_pkt->size, 1, fout);
+        int size = enc_pkt->size;
+        ret = fwrite(enc_pkt->data, 1, size, fout);
         av_packet_unref(enc_pkt);
-        if (ret != enc_pkt->size) {
+        if (ret != size) {
             ret = AVERROR(errno);
             break;
         }
-- 
2.49.1

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