On 3/20/2022 7:01 PM, Hendrik Leppkes wrote:
On Sun, Mar 20, 2022 at 7:52 PM James Almer <jamr...@gmail.com> wrote:

On 3/19/2022 4:50 AM, Hendrik Leppkes wrote:
On Sat, Mar 19, 2022 at 4:04 AM James Almer <jamr...@gmail.com> wrote:

The function is not meant to clear codec parameters, and the lavf demux code
relies on this behavior.
Regression since 327efa66331ebdc0087c6b656059a8df2f404019.

Signed-off-by: James Almer <jamr...@gmail.com>
---
   libavcodec/avcodec.c | 6 ++++++
   1 file changed, 6 insertions(+)

diff --git a/libavcodec/avcodec.c b/libavcodec/avcodec.c
index 38bdaad4fa..253c9f56cc 100644
--- a/libavcodec/avcodec.c
+++ b/libavcodec/avcodec.c
@@ -469,6 +469,7 @@ void avsubtitle_free(AVSubtitle *sub)

   av_cold int avcodec_close(AVCodecContext *avctx)
   {
+    AVChannelLayout ch_layout;
       int i;

       if (!avctx)
@@ -524,7 +525,12 @@ av_cold int avcodec_close(AVCodecContext *avctx)

       if (avctx->priv_data && avctx->codec && avctx->codec->priv_class)
           av_opt_free(avctx->priv_data);
+    /* av_opt_free() will uninitialize avctx->ch_layout, but we want to keep 
it.
+       It will be uninitialized in avcodec_free_context() */
+    ch_layout = avctx->ch_layout;
+    memset(&avctx->ch_layout, 0, sizeof(avctx->ch_layout));
       av_opt_free(avctx);
+    avctx->ch_layout = ch_layout;
       av_freep(&avctx->priv_data);
       if (av_codec_is_encoder(avctx->codec)) {
           av_freep(&avctx->extradata);

This feels pretty ugly and still a bit risky that any call to
av_opt_free could invalidate data its not supposed to. Maybe we should
have a flag for AVOptions instead where av_opt_free won't touch an
entry, because its only there to set/get it, not manage its memory?

Where would that flag be set? av_opt_free() takes none. And that
function exists purely to free strings, dictionaries, and now
uninitialize AVChannelLayout elements in a struct. If you don't want to
free what av_opt_set() allocated, you shouldn't call av_opt_free() at all.


On the AVOption element in the table, with the other AV_OPT_FLAG_*

Oh, you meant flagging the actual AVOption. My bad, i for some reason thought you meant having the user flag which options they wanted to "own".

I'll try to implement this. Any suggestion for the flag name? AV_OPT_FLAG_NO_FREE?

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