give context to av_log

Originally committed as revision 13593 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/imgresample.c

@@ -531,7 +531,7 @@ struct SwsContext *sws_getContext(int srcW, int srcH, int srcFormat,
 
     if ((srcH != dstH) || (srcW != dstW)) {
         if ((srcFormat != PIX_FMT_YUV420P) || (dstFormat != PIX_FMT_YUV420P)) {
-            av_log(NULL, AV_LOG_INFO, "PIX_FMT_YUV420P will be used as an intermediate format for rescaling\n");
+            av_log(ctx, AV_LOG_INFO, "PIX_FMT_YUV420P will be used as an intermediate format for rescaling\n");
         }
         ctx->resampling_ctx = img_resample_init(dstW, dstH, srcW, srcH);
     } else {
@@ -634,7 +634,7 @@ int sws_scale(struct SwsContext *ctx, uint8_t* src[], int srcStride[],
                             &src_pict, ctx->src_pix_fmt,
                             ctx->resampling_ctx->iwidth, ctx->resampling_ctx->iheight) < 0) {
 
-                av_log(NULL, AV_LOG_ERROR, "pixel format conversion not handled\n");
+                av_log(ctx, AV_LOG_ERROR, "pixel format conversion not handled\n");
                 res = -1;
                 goto the_end;
             }
@@ -673,7 +673,7 @@ int sws_scale(struct SwsContext *ctx, uint8_t* src[], int srcStride[],
                         resampled_picture, current_pix_fmt,
                         ctx->resampling_ctx->owidth, ctx->resampling_ctx->oheight) < 0) {
 
-            av_log(NULL, AV_LOG_ERROR, "pixel format conversion not handled\n");
+            av_log(ctx, AV_LOG_ERROR, "pixel format conversion not handled\n");
 
             res = -1;
             goto the_end;