[FFmpeg-devel] [PATCH] avcodec/pthread_frame: sync decoded_side_data arrays with all worker threads

[FFmpeg-devel] [PATCH] avcodec/pthread_frame: sync decoded_side_data arrays with all worker threads

[James Almer]

After being filled by FFCodec->init() from the first worker thread, it needs to
be copied to every other thread context. Otherwise, its entries will not be
present when ff_decode_frame_props() populates output frames.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/pthread_frame.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/libavcodec/pthread_frame.c b/libavcodec/pthread_frame.c
index 4ea5dd3698..7019108af6 100644
--- a/libavcodec/pthread_frame.c
+++ b/libavcodec/pthread_frame.c
@@ -905,6 +905,14 @@ static av_cold int init_thread(PerThreadContext *p, int *threads_to_free,
             if (err < 0)
                 return err;
         }
+    } else {
+        for (int i = 0; i < avctx->nb_decoded_side_data; i++) {
+            err = av_frame_side_data_clone(&copy->decoded_side_data,
+                                           &copy->nb_decoded_side_data,
+                                           avctx->decoded_side_data[i], 0);
+            if (err < 0)
+                return err;
+        }
     }
 
     atomic_init(&p->debug_threads, (copy->debug & FF_DEBUG_THREADS) != 0);
-- 
2.49.0

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[FFmpeg-devel] [PATCH 2/2] avcodec/decode: sync side_data_pref_mask across worker threads

[James Almer]

side_data_pref_mask is set during ff_decode_preinit() and then never copied to
worker threads. As such, any decoder calling one of the side data helpers that
rely on side_data_pref() in frame threaded scenarios will ignore the user set
list of side data types.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/decode.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index c2b2dd6e3b..20e99b3ffb 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -2209,6 +2209,7 @@ void ff_decode_internal_sync(AVCodecContext *dst, const AVCodecContext *src)
     const DecodeContext *src_dc = decode_ctx(src->internal);
     DecodeContext *dst_dc = decode_ctx(dst->internal);
 
+    dst_dc->side_data_pref_mask = src_dc->side_data_pref_mask;
     av_refstruct_replace(&dst_dc->lcevc, src_dc->lcevc);
 }
 
-- 
2.49.0

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Re: [FFmpeg-devel] [PATCH 2/2] avcodec/decode: sync side_data_pref_mask across worker threads

[Andreas Rheinhardt]

James Almer:
> side_data_pref_mask is set during ff_decode_preinit() and then never copied to
> worker threads. As such, any decoder calling one of the side data helpers that
> rely on side_data_pref() in frame threaded scenarios will ignore the user set
> list of side data types.
> 
> Signed-off-by: James Almer <jamrial@gmail.com>
> ---
>  libavcodec/decode.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
> index c2b2dd6e3b..20e99b3ffb 100644
> --- a/libavcodec/decode.c
> +++ b/libavcodec/decode.c
> @@ -2209,6 +2209,7 @@ void ff_decode_internal_sync(AVCodecContext *dst, const AVCodecContext *src)
>      const DecodeContext *src_dc = decode_ctx(src->internal);
>      DecodeContext *dst_dc = decode_ctx(dst->internal);
>  
> +    dst_dc->side_data_pref_mask = src_dc->side_data_pref_mask;
>      av_refstruct_replace(&dst_dc->lcevc, src_dc->lcevc);
>  }
>  

Why is this done for every frame, even though it does not change after
preinit?

- Andreas

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Re: [FFmpeg-devel] [PATCH 2/2] avcodec/decode: sync side_data_pref_mask across worker threads

[James Almer]

[-- Attachment #1.1.1: Type: text/plain, Size: 1232 bytes --]

On 4/27/2025 3:52 PM, Andreas Rheinhardt wrote:
> James Almer:
>> side_data_pref_mask is set during ff_decode_preinit() and then never copied to
>> worker threads. As such, any decoder calling one of the side data helpers that
>> rely on side_data_pref() in frame threaded scenarios will ignore the user set
>> list of side data types.
>>
>> Signed-off-by: James Almer <jamrial@gmail.com>
>> ---
>>   libavcodec/decode.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/libavcodec/decode.c b/libavcodec/decode.c
>> index c2b2dd6e3b..20e99b3ffb 100644
>> --- a/libavcodec/decode.c
>> +++ b/libavcodec/decode.c
>> @@ -2209,6 +2209,7 @@ void ff_decode_internal_sync(AVCodecContext *dst, const AVCodecContext *src)
>>       const DecodeContext *src_dc = decode_ctx(src->internal);
>>       DecodeContext *dst_dc = decode_ctx(dst->internal);
>>   
>> +    dst_dc->side_data_pref_mask = src_dc->side_data_pref_mask;
>>       av_refstruct_replace(&dst_dc->lcevc, src_dc->lcevc);
>>   }
>>   
> 
> Why is this done for every frame, even though it does not change after
> preinit?

I think the ff_decode_internal_sync() call in 
update_context_from_thread() from pthread_frame.c could be removed?


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