fftools/ffmpeg: replace print_error() by more meaningful messages

fftools/ffmpeg.c

@@ -1756,12 +1756,10 @@ static void decode_flush(InputFile *ifile)
 static int process_input(int file_index)
 {
     InputFile *ifile = input_files[file_index];
-    AVFormatContext *is;
     InputStream *ist;
     AVPacket *pkt;
     int ret, i;
 
-    is  = ifile->ctx;
     ret = ifile_get_packet(ifile, &pkt);
 
     if (ret == AVERROR(EAGAIN)) {
@@ -1775,7 +1773,8 @@ static int process_input(int file_index)
     }
     if (ret < 0) {
         if (ret != AVERROR_EOF) {
-            print_error(is->url, ret);
+            av_log(ifile, AV_LOG_ERROR,
+                   "Error retrieving a packet from demuxer: %s\n", av_err2str(ret));
             if (exit_on_error)
                 exit_program(1);
         }

fftools/ffmpeg_demux.c

@@ -1405,7 +1405,8 @@ int ifile_open(const OptionsContext *o, const char *filename)
     /* open the input file with generic avformat function */
     err = avformat_open_input(&ic, filename, file_iformat, &o->g->format_opts);
     if (err < 0) {
-        print_error(filename, err);
+        av_log(d, AV_LOG_ERROR,
+               "Error opening input: %s\n", av_err2str(err));
         if (err == AVERROR_PROTOCOL_NOT_FOUND)
             av_log(d, AV_LOG_ERROR, "Did you mean file:%s?\n", filename);
         exit_program(1);

fftools/ffmpeg_mux.c

@@ -139,7 +139,9 @@ static int write_packet(Muxer *mux, OutputStream *ost, AVPacket *pkt)
 
     ret = av_interleaved_write_frame(s, pkt);
     if (ret < 0) {
-        print_error("av_interleaved_write_frame()", ret);
+        av_log(ost, AV_LOG_ERROR,
+               "Error submitting a packet to the muxer: %s\n",
+               av_err2str(ret));
         goto fail;
     }