@@ -1990,7 +1990,7 @@ static int transcode(AVFormatContext **output_files,

     nb_ostreams = 0;

     for(i=0;i<nb_output_files;i++) {

         os = output_files[i];

-        if (!os->nb_streams) {

+        if (!os->nb_streams && !(os->oformat->flags & AVFMT_NOSTREAMS)) {

             dump_format(output_files[i], i, output_files[i]->filename, 1);

             fprintf(stderr, "Output file #%d does not contain any stream\n", i);

             ret = AVERROR(EINVAL);

@@ -323,6 +323,7 @@ typedef struct AVFormatParameters {

 #define AVFMT_TS_DISCONT    0x0200 /**< Format allows timestamp discontinuities. Note, muxers always require valid (monotone) timestamps */

 #define AVFMT_VARIABLE_FPS  0x0400 /**< Format allows variable fps. */

 #define AVFMT_NODIMENSIONS  0x0800 /**< Format does not need width/height */

+#define AVFMT_NOSTREAMS     0x1000 /**< Format does not require any streams */

 typedef struct AVOutputFormat {

     const char *name;

@@ -2709,7 +2709,7 @@ int av_write_header(AVFormatContext *s)

     AVStream *st;

     // some sanity checks

-    if (s->nb_streams == 0) {

+    if (s->nb_streams == 0 && !(s->oformat->flags & AVFMT_NOSTREAMS)) {

         av_log(s, AV_LOG_ERROR, "no streams\n");

         return AVERROR(EINVAL);

     }

@@ -2777,7 +2777,7 @@ int av_write_header(AVFormatContext *s)

 #endif

     /* set muxer identification string */

-    if (!(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT)) {

+    if (s->nb_streams && !(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT)) {

         av_metadata_set2(&s->metadata, "encoder", LIBAVFORMAT_IDENT, 0);

     }