avconv: do not overwrite the stream codec context for streamcopy

Since we are not doing encoding, there is no point in ever touching the
separate encoding context. Always use the stream codec context.

Fixes writing attachments.

CC:libav-devel@libav.org

avconv.c

@@ -318,7 +318,7 @@ static void update_sample_fmt(AVCodecContext *dec, AVCodec *dec_codec,
 static void write_frame(AVFormatContext *s, AVPacket *pkt, OutputStream *ost)
 {
     AVBitStreamFilterContext *bsfc = ost->bitstream_filters;
-    AVCodecContext          *avctx = ost->enc_ctx;
+    AVCodecContext          *avctx = ost->encoding_needed ? ost->enc_ctx : ost->st->codec;
     int ret;
 
     /*
@@ -1706,7 +1706,7 @@ static int transcode_init(void)
         if (ost->attachment_filename)
             continue;
 
-        enc_ctx = ost->enc_ctx;
+        enc_ctx = ost->stream_copy ? ost->st->codec : ost->enc_ctx;
 
         if (ist) {
             dec_ctx = ist->dec_ctx;
@@ -1985,20 +1985,21 @@ static int transcode_init(void)
             if (ost->enc_ctx->bit_rate && ost->enc_ctx->bit_rate < 1000)
                 av_log(NULL, AV_LOG_WARNING, "The bitrate parameter is set too low."
                                              "It takes bits/s as argument, not kbits/s\n");
+
+            ret = avcodec_copy_context(ost->st->codec, ost->enc_ctx);
+            if (ret < 0) {
+                av_log(NULL, AV_LOG_FATAL,
+                       "Error initializing the output stream codec context.\n");
+                exit_program(1);
+            }
+
+            ost->st->time_base = ost->enc_ctx->time_base;
         } else {
             ret = av_opt_set_dict(ost->enc_ctx, &ost->encoder_opts);
             if (ret < 0)
                 return ret;
+            ost->st->time_base = ost->st->codec->time_base;
         }
-
-        ret = avcodec_copy_context(ost->st->codec, ost->enc_ctx);
-        if (ret < 0) {
-            av_log(NULL, AV_LOG_FATAL,
-                   "Error initializing the output stream codec context.\n");
-            exit_program(1);
-        }
-
-        ost->st->time_base = ost->enc_ctx->time_base;
     }
 
     /* init input streams */