diff --git a/libavformat/a64.c b/libavformat/a64.c
index 32ed00b063..ad41cdc8c0 100644
--- a/libavformat/a64.c
+++ b/libavformat/a64.c
@@ -24,9 +24,16 @@
 #include "libavcodec/bytestream.h"
 #include "avformat.h"
 
+typedef struct A64MuxerContext {
+    int interleaved;
+    AVPacket prev_pkt;
+    int prev_frame_count;
+} A64MuxerContext;
+
 static int a64_write_header(struct AVFormatContext *s)
 {
     AVCodecContext *avctx=s->streams[0]->codec;
+    A64MuxerContext *c = s->priv_data;
     uint8_t header[5] = {
         0x00, //load
         0x40, //address
@@ -34,6 +41,7 @@ static int a64_write_header(struct AVFormatContext *s)
         0x00, //charset_lifetime (multi only)
         0x00  //fps in 50/fps;
     };
+    c->interleaved = 0;
     switch (avctx->codec->id) {
     case CODEC_ID_A64_MULTI:
         header[2] = 0x00;
@@ -50,16 +58,99 @@ static int a64_write_header(struct AVFormatContext *s)
         break;
     }
     put_buffer(s->pb, header, 2);
+    c->prev_pkt.size = 0;
+    c->prev_frame_count = 0;
     return 0;
 }
 
 static int a64_write_packet(struct AVFormatContext *s, AVPacket *pkt)
 {
-    put_buffer(s->pb, pkt->data, pkt->size);
+    AVCodecContext *avctx = s->streams[0]->codec;
+    A64MuxerContext *c = s->priv_data;
+    int i, j;
+    int ch_chunksize;
+    int lifetime;
+    int frame_count;
+    int charset_size;
+    int frame_size;
+    int num_frames;
+
+    /* fetch values from extradata */
+    switch (avctx->codec->id) {
+    case CODEC_ID_A64_MULTI:
+    case CODEC_ID_A64_MULTI5:
+        if(c->interleaved) {
+            /* Write interleaved, means we insert chunks of the future charset before each current frame.
+             * Reason: if we load 1 charset + corresponding frames in one block on c64, we need to store
+             * them first and then display frame by frame to keep in sync. Thus we would read and write
+             * the data for colram from/to ram first and waste too much time. If we interleave and send the
+             * charset beforehand, we assemble a new charset chunk by chunk, write current screen data to
+             * screen-ram to be displayed and decode the colram directly to colram-location $d800 during
+             * the overscan, while reading directly from source
+             * This is the only way so far, to achieve 25fps on c64 */
+            if(avctx->extradata) {
+                /* fetch values from extradata */
+                lifetime     = AV_RB32(avctx->extradata + 0);
+                frame_count  = AV_RB32(avctx->extradata + 4);
+                charset_size = AV_RB32(avctx->extradata + 8);
+                frame_size   = AV_RB32(avctx->extradata + 12);
+
+                /* TODO: sanity checks? */
+            }
+            else {
+                av_log(avctx, AV_LOG_ERROR, "extradata not set\n");
+                return AVERROR(EINVAL);
+            }
+            ch_chunksize=charset_size/lifetime;
+            /* TODO: check if charset/size is % lifetime, but maybe check in codec */
+            if(pkt->data) num_frames = lifetime;
+            else num_frames = c->prev_frame_count;
+            for(i = 0; i < num_frames; i++) {
+                if(pkt->data) {
+                    /* if available, put newest charset chunk into buffer */
+                    put_buffer(s->pb, pkt->data + ch_chunksize * i, ch_chunksize);
+                }
+                else {
+                       /* a bit ugly, but is there an alternative to put many zeros? */
+                        for(j = 0; j < ch_chunksize; j++) put_byte(s->pb, 0);
+                }
+                if(c->prev_pkt.data) {
+                    /* put frame (screen + colram) from last packet into buffer */
+                    put_buffer(s->pb, c->prev_pkt.data + charset_size + frame_size * i, frame_size);
+                }
+                else {
+                       /* a bit ugly, but is there an alternative to put many zeros? */
+                        for(j = 0; j < frame_size; j++) put_byte(s->pb, 0);
+                }
+            }
+            /* backup current packet for next turn */
+            if(pkt->data) {
+                av_new_packet(&c->prev_pkt, pkt->size);
+                memcpy(c->prev_pkt.data, pkt->data, pkt->size);
+            }
+            c->prev_frame_count = frame_count;
+            break;
+        }
+        default:
+            /* Write things as is. Nice for self-contained frames from non-multicolor modes or if played
+             * directly from ram and not from a streaming device (rrnet/mmc) */
+            if(pkt) put_buffer(s->pb, pkt->data, pkt->size);
+        break;
+    }
+
     put_flush_packet(s->pb);
     return 0;
 }
 
+static int a64_write_trailer(struct AVFormatContext *s)
+{
+    A64MuxerContext *c = s->priv_data;
+    AVPacket pkt;
+    /* need to flush last packet? */
+    if(c->interleaved) a64_write_packet(s, &pkt);
+    return 0;
+}
+
 AVOutputFormat a64_muxer = {
     .name = "a64",
     .long_name = NULL_IF_CONFIG_SMALL("a64 - video for Commodore 64"),
@@ -69,4 +160,5 @@ AVOutputFormat a64_muxer = {
     .video_codec = CODEC_ID_A64_MULTI,
     a64_write_header,
     a64_write_packet,
+    a64_write_trailer
 };