avconv: pass the hw context from filters to the encoder

avconv.c

@@ -1581,6 +1581,12 @@ static int init_output_stream(OutputStream *ost, char *error, int error_len)
         if (!av_dict_get(ost->encoder_opts, "threads", NULL, 0))
             av_dict_set(&ost->encoder_opts, "threads", "auto", 0);
 
+        if (ost->filter && ost->filter->filter->inputs[0]->hw_frames_ctx) {
+            ost->enc_ctx->hw_frames_ctx = av_buffer_ref(ost->filter->filter->inputs[0]->hw_frames_ctx);
+            if (!ost->enc_ctx->hw_frames_ctx)
+                return AVERROR(ENOMEM);
+        }
+
         if ((ret = avcodec_open2(ost->enc_ctx, codec, &ost->encoder_opts)) < 0) {
             if (ret == AVERROR_EXPERIMENTAL)
                 abort_codec_experimental(codec, 1);