diff --git a/fftools/ffmpeg_mux.c b/fftools/ffmpeg_mux.c
index 032b2ac34c..4ad69a149a 100644
--- a/fftools/ffmpeg_mux.c
+++ b/fftools/ffmpeg_mux.c
@@ -45,6 +45,11 @@ static Muxer *mux_from_of(OutputFile *of)
     return (Muxer*)of;
 }
 
+static MuxStream *ms_from_ost(OutputStream *ost)
+{
+    return (MuxStream*)ost;
+}
+
 static int64_t filesize(AVIOContext *pb)
 {
     int64_t ret = -1;
@@ -60,7 +65,7 @@ static int64_t filesize(AVIOContext *pb)
 
 static int write_packet(Muxer *mux, OutputStream *ost, AVPacket *pkt)
 {
-    MuxStream *ms = &mux->streams[ost->index];
+    MuxStream *ms = ms_from_ost(ost);
     AVFormatContext *s = mux->fc;
     AVStream *st = ost->st;
     int64_t fs;
@@ -251,7 +256,7 @@ finish:
 
 static int queue_packet(Muxer *mux, OutputStream *ost, AVPacket *pkt)
 {
-    MuxStream *ms = &mux->streams[ost->index];
+    MuxStream *ms = ms_from_ost(ost);
     AVPacket *tmp_pkt = NULL;
     int ret;
 
@@ -409,8 +414,8 @@ static int thread_start(Muxer *mux)
 
     /* flush the muxing queues */
     for (int i = 0; i < fc->nb_streams; i++) {
-        MuxStream     *ms = &mux->streams[i];
         OutputStream *ost = mux->of.streams[i];
+        MuxStream     *ms = ms_from_ost(ost);
         AVPacket *pkt;
 
         /* try to improve muxing time_base (only possible if nothing has been written yet) */
@@ -626,9 +631,11 @@ int of_write_trailer(OutputFile *of)
 static void ost_free(OutputStream **post)
 {
     OutputStream *ost = *post;
+    MuxStream *ms;
 
     if (!ost)
         return;
+    ms = ms_from_ost(ost);
 
     if (ost->logfile) {
         if (fclose(ost->logfile))
@@ -638,6 +645,13 @@ static void ost_free(OutputStream **post)
         ost->logfile = NULL;
     }
 
+    if (ms->muxing_queue) {
+        AVPacket *pkt;
+        while (av_fifo_read(ms->muxing_queue, &pkt, 1) >= 0)
+            av_packet_free(&pkt);
+        av_fifo_freep2(&ms->muxing_queue);
+    }
+
     av_bsf_free(&ost->bsf_ctx);
 
     av_frame_free(&ost->filtered_frame);
@@ -697,19 +711,6 @@ void of_close(OutputFile **pof)
     sq_free(&of->sq_encode);
     sq_free(&mux->sq_mux);
 
-    for (int i = 0; i < mux->nb_streams; i++) {
-        MuxStream *ms = &mux->streams[i];
-        AVPacket *pkt;
-
-        if (!ms->muxing_queue)
-            continue;
-
-        while (av_fifo_read(ms->muxing_queue, &pkt, 1) >= 0)
-            av_packet_free(&pkt);
-        av_fifo_freep2(&ms->muxing_queue);
-    }
-    av_freep(&mux->streams);
-
     for (int i = 0; i < of->nb_streams; i++)
         ost_free(&of->streams[i]);
     av_freep(&of->streams);
diff --git a/fftools/ffmpeg_mux.h b/fftools/ffmpeg_mux.h
index b73b6c628b..45daeb3591 100644
--- a/fftools/ffmpeg_mux.h
+++ b/fftools/ffmpeg_mux.h
@@ -35,6 +35,8 @@
 #include "libavutil/thread.h"
 
 typedef struct MuxStream {
+    OutputStream ost;
+
     /* the packets are buffered here until the muxer is ready to be initialized */
     AVFifo *muxing_queue;
 
@@ -57,9 +59,6 @@ typedef struct Muxer {
     pthread_t    thread;
     ThreadQueue *tq;
 
-    MuxStream *streams;
-    int     nb_streams;
-
     AVDictionary *opts;
 
     int thread_queue_size;
diff --git a/fftools/ffmpeg_mux_init.c b/fftools/ffmpeg_mux_init.c
index 6909a017d8..d6bae92513 100644
--- a/fftools/ffmpeg_mux_init.c
+++ b/fftools/ffmpeg_mux_init.c
@@ -168,6 +168,7 @@ static OutputStream *new_output_stream(Muxer *mux, OptionsContext *o,
                                        enum AVMediaType type, int source_index)
 {
     AVFormatContext *oc = mux->fc;
+    MuxStream     *ms;
     OutputStream *ost;
     const AVCodec *enc;
     AVStream *st = avformat_new_stream(oc, NULL);
@@ -183,7 +184,14 @@ static OutputStream *new_output_stream(Muxer *mux, OptionsContext *o,
     if (oc->nb_streams - 1 < o->nb_streamid_map)
         st->id = o->streamid_map[oc->nb_streams - 1];
 
-    ost = ALLOC_ARRAY_ELEM(mux->of.streams, mux->of.nb_streams);
+    ms  = allocate_array_elem(&mux->of.streams, sizeof(MuxStream),
+                              &mux->of.nb_streams);
+    ost = &ms->ost;
+
+    ms->muxing_queue = av_fifo_alloc2(8, sizeof(AVPacket*), 0);
+    if (!ms->muxing_queue)
+        report_and_exit(AVERROR(ENOMEM));
+    ms->last_mux_dts = AV_NOPTS_VALUE;
 
     ost->file_index = nb_output_files - 1;
     ost->index      = idx;
@@ -1900,19 +1908,6 @@ int of_open(OptionsContext *o, const char *filename)
 
     of->url        = filename;
 
-    mux->streams = av_calloc(oc->nb_streams, sizeof(*mux->streams));
-    if (!mux->streams)
-        return AVERROR(ENOMEM);
-    mux->nb_streams = oc->nb_streams;
-
-    for (int i = 0; i < mux->nb_streams; i++) {
-        MuxStream *ms = &mux->streams[i];
-        ms->muxing_queue = av_fifo_alloc2(8, sizeof(AVPacket*), 0);
-        if (!ms->muxing_queue)
-            return AVERROR(ENOMEM);
-        ms->last_mux_dts = AV_NOPTS_VALUE;
-    }
-
     /* write the header for files with no streams */
     if (of->format->flags & AVFMT_NOSTREAMS && oc->nb_streams == 0) {
         int ret = mux_check_init(mux);