avformat/dashenc: Added an option to ignore io errors

When dashenc has to run for long duration(say 24x7 live stream), one can enable this option to ignore the io failure of few segment's upload due to an intermittent network issues.
When the network connection recovers dashenc will continue with the upload of the current segments, leading to the recovery of the stream.

doc/muxers.texi

@@ -300,6 +300,9 @@ If this flag is set, the dash segment files will be in in ISOBMFF format.
 @item webm
 If this flag is set, the dash segment files will be in in WebM format.
 
+@item -ignore_io_errors @var{ignore_io_errors}
+Ignore IO errors during open and write. Useful for long-duration runs with network output.
+
 @end table
 
 @anchor{framecrc}

libavformat/dashenc.c

@@ -138,6 +138,7 @@ typedef struct DASHContext {
     int index_correction;
     char *format_options_str;
     SegmentType segment_type_option;  /* segment type as specified in options */
+    int ignore_io_errors;
 } DASHContext;
 
 static struct codec_string {
@@ -853,7 +854,7 @@ static int write_manifest(AVFormatContext *s, int final)
     av_dict_free(&opts);
     if (ret < 0) {
         av_log(s, AV_LOG_ERROR, "Unable to open %s for writing\n", temp_filename);
-        return ret;
+        return c->ignore_io_errors ? 0 : ret;
     }
     out = c->mpd_out;
     avio_printf(out, "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n");
@@ -944,7 +945,7 @@ static int write_manifest(AVFormatContext *s, int final)
         av_dict_free(&opts);
         if (ret < 0) {
             av_log(s, AV_LOG_ERROR, "Unable to open %s for writing\n", temp_filename);
-            return ret;
+            return c->ignore_io_errors ? 0 : ret;
         }
 
         ff_hls_write_playlist_version(c->m3u8_out, 7);
@@ -1576,8 +1577,9 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
         set_http_options(&opts, c);
         ret = dashenc_io_open(s, &os->out, os->temp_path, &opts);
         av_dict_free(&opts);
-        if (ret < 0)
+        if (ret < 0) {
-            return ret;
+            return c->ignore_io_errors ? 0 : ret;
+        }
     }
 
     //write out the data immediately in streaming mode
@@ -1588,9 +1590,11 @@ static int dash_write_packet(AVFormatContext *s, AVPacket *pkt)
             write_styp(os->ctx->pb);
         avio_flush(os->ctx->pb);
         len = avio_get_dyn_buf (os->ctx->pb, &buf);
-        avio_write(os->out, buf + os->written_len, len - os->written_len);
+        if (os->out) {
+            avio_write(os->out, buf + os->written_len, len - os->written_len);
+            avio_flush(os->out);
+        }
         os->written_len = len;
-        avio_flush(os->out);
     }
 
     return ret;
@@ -1693,6 +1697,7 @@ static const AVOption options[] = {
     { "auto", "select segment file format based on codec", 0, AV_OPT_TYPE_CONST, {.i64 = SEGMENT_TYPE_AUTO }, 0, UINT_MAX,   E, "segment_type"},
     { "mp4", "make segment file in ISOBMFF format", 0, AV_OPT_TYPE_CONST, {.i64 = SEGMENT_TYPE_MP4 }, 0, UINT_MAX,   E, "segment_type"},
     { "webm", "make segment file in WebM format", 0, AV_OPT_TYPE_CONST, {.i64 = SEGMENT_TYPE_WEBM }, 0, UINT_MAX,   E, "segment_type"},
+    { "ignore_io_errors", "Ignore IO errors during open and write. Useful for long-duration runs with network output", OFFSET(ignore_io_errors), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, E },
     { NULL },
 };