[FFmpeg-devel] [PATCH 08/12] lavc/frame_thread_encoder: avoid assigning a whole AVCodecContext

[Andreas Rheinhardt]

Anton Khirnov:
> It is highly unsafe, as AVCodecContext contains many allocated fields.
> Copying information via AVCodecParameters and with av_opt_copy() should
> handle everything needed by thread workers.
> ---
>  libavcodec/frame_thread_encoder.c | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/libavcodec/frame_thread_encoder.c b/libavcodec/frame_thread_encoder.c
> index cda5158117..744062b776 100644
> --- a/libavcodec/frame_thread_encoder.c
> +++ b/libavcodec/frame_thread_encoder.c
> @@ -28,6 +28,7 @@
>  #include "libavutil/thread.h"
>  #include "avcodec.h"
>  #include "avcodec_internal.h"
> +#include "codec_par.h"
>  #include "encode.h"
>  #include "internal.h"
>  #include "pthread_internal.h"
> @@ -121,6 +122,7 @@ av_cold int ff_frame_thread_encoder_init(AVCodecContext *avctx)
>      int i=0;
>      ThreadContext *c;
>      AVCodecContext *thread_avctx = NULL;
> +    AVCodecParameters *par = NULL;
>      int ret;
>  
>      if(   !(avctx->thread_type & FF_THREAD_FRAME)
> @@ -194,18 +196,27 @@ av_cold int ff_frame_thread_encoder_init(AVCodecContext *avctx)
>          }
>      }
>  
> +    par = avcodec_parameters_alloc();
> +    if (!par) {
> +        ret = AVERROR(ENOMEM);
> +        goto fail;
> +    }
> +
> +    ret = avcodec_parameters_from_context(par, avctx);
> +    if (ret < 0)
> +        goto fail;
> +
>      for(i=0; i<avctx->thread_count ; i++){
> -        void *tmpv;
>          thread_avctx = avcodec_alloc_context3(avctx->codec);
>          if (!thread_avctx) {
>              ret = AVERROR(ENOMEM);
>              goto fail;
>          }
> -        tmpv = thread_avctx->priv_data;
> -        *thread_avctx = *avctx;
> -        thread_avctx->priv_data = tmpv;
> -        thread_avctx->internal = NULL;
> -        thread_avctx->hw_frames_ctx = NULL;
> +
> +        ret = avcodec_parameters_to_context(thread_avctx, par);
> +        if (ret < 0)
> +            goto fail;
> +
>          ret = av_opt_copy(thread_avctx, avctx);
>          if (ret < 0)
>              goto fail;
> @@ -227,10 +238,13 @@ av_cold int ff_frame_thread_encoder_init(AVCodecContext *avctx)
>          }
>      }
>  
> +    avcodec_parameters_free(&par);
> +
>      avctx->active_thread_type = FF_THREAD_FRAME;
>  
>      return 0;
>  fail:
> +    avcodec_parameters_free(&par);
>      ff_codec_close(thread_avctx);
>      av_freep(&thread_avctx);
>      avctx->thread_count = i;

IIRC the mjpeg encoders use intra_matrix and this will now no longer be
copied to the worker threads.

- Andreas