diff --git a/assets/disk0/home/mp3test.js b/assets/disk0/home/mp3test.js
index 4428df6..ae2a8a9 100644
--- a/assets/disk0/home/mp3test.js
+++ b/assets/disk0/home/mp3test.js
@@ -2,22 +2,90 @@ const Mp3 = require('mp3dec')
 const pcm = require("pcm")
 
 
+class SequentialFileBuffer {
+
+    constructor(path, offset, length) {
+        if (Array.isArray(path)) throw Error("arg #1 is path(string), not array")
+
+        this.path = path
+        this.file = files.open(path)
+
+        this.offset = offset || 0
+        this.originalOffset = offset
+        this.length = length || this.file.size
+
+        this.seq = require("seqread")
+        this.seq.prepare(path)
+    }
+
+    /*readFull(n) {
+        throw Error()
+        let ptr = this.seq.readBytes(n)
+        return ptr
+    }*/
+
+    readStr(n) {
+        let ptr = this.seq.readBytes(n)
+        let s = ''
+        for (let i = 0; i < n; i++) {
+            if (i >= this.length) break
+            s += String.fromCharCode(sys.peek(ptr + i))
+        }
+        sys.free(ptr)
+        return s
+    }
+
+    readByteNumbers(n) {
+        let ptr = this.seq.readBytes(n)
+        let s = []
+        for (let i = 0; i < n; i++) {
+            if (i >= this.length) break
+            s.push(sys.peek(ptr + i))
+        }
+        sys.free(ptr)
+        return s
+    }
+
+    unread(diff) {
+        let newSkipLen = this.seq.getReadCount() - diff
+        this.seq.prepare(this.path)
+        this.seq.skip(newSkipLen)
+    }
+
+    rewind() {
+        this.seq.prepare(this.path)
+    }
+
+    seek(p) {
+        this.seq.prepare(this.path)
+        this.seq.skip(p)
+    }
+
+    get byteLength() {
+        return this.length
+    }
+
+    /*get remaining() {
+        return this.length - this.getReadCount()
+    }*/
+}
+
+
+
 Object.keys(Mp3).forEach(e=>{
     print(`${e}\t`)
 })
 println()
 
 println("reading...")
-let arr = files.open("A:/gateless.mp3").bread()
-let ab = new ArrayBuffer(arr.length)
-let abba = new Uint8Array(ab)
-arr.forEach((v,i)=>{ abba[i] = v })
-
-
-let mp3ArrayBuffer = new Uint8Array(ab, 0, arr.length)
+//let arr = files.open("A:/gateless.mp3").bread()
+//let ab = new ArrayBuffer(arr.length)
+//let abba = new Uint8Array(ab)
+//arr.forEach((v,i)=>{ abba[i] = v })
+//let mp3ArrayBuffer = new Uint8Array(ab, 0, arr.length)*
 
 println("decoding...")
-let decoder = Mp3.newDecoder(ab)
+let decoder = Mp3.newDecoder(new SequentialFileBuffer("A:/gateless0.mp3"))
 if (decoder === null) throw Error("decoder is null")
 
 audio.resetParams(0)
@@ -47,7 +115,11 @@ function printPlayBar() {
 
 
 const QUEUE_MAX = 4
+let t1 = sys.nanoTime()
 decoder.decode(obj=>{
+    let t2 = sys.nanoTime()
+
+
     let buf = obj.buf
     let err = obj.err
 
@@ -60,8 +132,16 @@ decoder.decode(obj=>{
     audio.startSampleUpload(0)
     audio.play(0)
 
-    serial.println(`Send sample (${audio.getPosition(0)})`)
-//    sys.sleep(0) // decoding time is slower than realtime :(
+
+//    sys.sleep(10) // decoding time is slower than realtime :(
+
+
+    let decodingTime = t2 - t1
+    let bufRealTimeLen = (declen) / 64000.0 * 1000000000
+    t1 = t2
+    println(`Decoded ${decodedLength} bytes; lag: ${(decodingTime - bufRealTimeLen) / 1000000} ms`)
+
+
 
 
 }) // now you got decoded PCM data
diff --git a/assets/disk0/tvdos/include/js-mp3/frame.js b/assets/disk0/tvdos/include/js-mp3/frame.js
index 6dbc58e..c605f42 100644
--- a/assets/disk0/tvdos/include/js-mp3/frame.js
+++ b/assets/disk0/tvdos/include/js-mp3/frame.js
@@ -643,14 +643,8 @@ var Frame = {
     },
 
     readCRC: function (source) {
-        var result = source.readFull(2);
-        if (result.err) {
-            return {
-                err: result.err
-            }
-        }
-        var buf = result.buf;
-        if (buf.byteLength < 2) {
+        var buf = source.readFull(2)
+        if (buf.length < 2) {
             return "mp3: error at readCRC";
         }
     },
diff --git a/assets/disk0/tvdos/include/js-mp3/frameheader.js b/assets/disk0/tvdos/include/js-mp3/frameheader.js
index 2716116..9d7d7d8 100644
--- a/assets/disk0/tvdos/include/js-mp3/frameheader.js
+++ b/assets/disk0/tvdos/include/js-mp3/frameheader.js
@@ -2,6 +2,7 @@ var consts = require('A:/tvdos/include/js-mp3/consts.js');
 
 var Frameheader = {
     createNew: function (value) {
+
         // A mepg1FrameHeader is MPEG1 Layer 1-3 frame header
         var fh = {
             value: value
@@ -214,14 +215,8 @@ var Frameheader = {
     read: function (source, position) {
         var pos = position;
 
-        var result = source.readFull(4);
-        if (result.err) {
-            return {
-                err: result.err
-            }
-        }
-        var buf = result.buf;
-        if (buf.byteLength < 4) {
+        var buf = source.readFull(4)
+        if (buf.length < 4) {
             return {
                 h: 0,
                 position: 0,
@@ -238,15 +233,9 @@ var Frameheader = {
         while (!fh.isValid()) {
             // stopPosition++;
 
-            result = source.readFull(1);
-            if (result.err) {
-                return {
-                    err: result.err
-                }
-            }
-            buf = result.buf;
+            buf = source.readFull(1);
 
-            if (buf.byteLength < 1) {
+            if (buf.length < 1) {
                 return {
                     h: 0,
                     position: 0,
diff --git a/assets/disk0/tvdos/include/js-mp3/maindata.js b/assets/disk0/tvdos/include/js-mp3/maindata.js
index 6cd983d..86cce5f 100644
--- a/assets/disk0/tvdos/include/js-mp3/maindata.js
+++ b/assets/disk0/tvdos/include/js-mp3/maindata.js
@@ -186,23 +186,24 @@ var read = function (source, prev, size, offset) {
     if (prev !== null) {
         vec = prev.Tail(offset);
     }
+
+
+
+//    serial.println(`maindata readFull(${size})`)
+
     // Read the main_data from file
-    var result = source.readFull(size);
-    if (result.err) {
-        return {
-            err: result.err
-        }
-    }
-    var buf = result.buf;
+    var buf = source.readFull(size);
     // var buf = new Uint8Array(source, 0, size);
-    if (buf.byteLength < size) {
+    if (buf.length < size) {
         return {
             b: null,
             err: "maindata.Read (2)"
         }
     }
+
     return {
-        b: bits.createNew(util.concatBuffers(vec, new Uint8Array(buf.slice()).buffer)),
+//        b: bits.createNew(util.concatBuffers(vec, new Uint8Array(buf.slice()).buffer)),
+        b: bits.createNew(util.concatBuffers(vec, new Uint8Array(buf).buffer)),
         err: null
     }
 };
diff --git a/assets/disk0/tvdos/include/js-mp3/sideinfo.js b/assets/disk0/tvdos/include/js-mp3/sideinfo.js
index e2d1404..4ca22c7 100644
--- a/assets/disk0/tvdos/include/js-mp3/sideinfo.js
+++ b/assets/disk0/tvdos/include/js-mp3/sideinfo.js
@@ -73,23 +73,21 @@ var Sideinfo = {
         if (fheader.protectionBit() === 0) {
             main_data_size -= 2;
         }
+
+
+//        serial.println(`sideinfo readFull(${sideinfo_size})`)
+
         // Read sideinfo from bitstream into buffer used by Bits()
-        var result = source.readFull(sideinfo_size);
-        if (result.err) {
-            return {
-                err: result.err
-            }
-        }
-        var buf = result.buf;
+        var buf = source.readFull(sideinfo_size);
         // var buf = new Uint8Array(source.buf, pos, sideinfo_size);
-        if (buf.byteLength < sideinfo_size) {
+        if (buf.length < sideinfo_size) {
             return {
                 v: null,
                 pos: pos,
                 err: "mp3: couldn't read sideinfo " + sideinfo_size + " bytes"
             }
         }
-        var s = Bits.createNew(new Uint8Array(buf.slice()).buffer);
+        var s = Bits.createNew(new Uint8Array(buf).buffer);
 
         // Parse audio data
         // Pointer to where we should start reading main data
diff --git a/assets/disk0/tvdos/include/mp3dec.js b/assets/disk0/tvdos/include/mp3dec.js
index 9056bf5..cbadafe 100644
--- a/assets/disk0/tvdos/include/mp3dec.js
+++ b/assets/disk0/tvdos/include/mp3dec.js
@@ -53,6 +53,7 @@ var Mp3 = {
                     err: "position not correct"
                 }
             }
+            source.buf.seek(position)
             source.pos = position;
             return {
                 pos: source.pos
@@ -60,35 +61,23 @@ var Mp3 = {
         };
 
         source.readFull = function (length) {
+            if (length < 0) throw Error("Source.pos less than 0: "+source.pos)
 
-            try {
-                if (length < 0) throw Error("Source.pos less than 0: "+source.pos)
+            var l = Math.min(source.buf.byteLength - source.pos, length);
 
-                var l = Math.min(source.buf.byteLength - source.pos, length);
-
-                if (l < 0) {
-                    serial.println("l < 0: "+l)
-                    throw Error("l < 0: "+l)
-                }
-
-                var bbuf = new Uint8Array(source.buf, source.pos, l);
-
-                source.pos += bbuf.byteLength;
-
-                if (source.pos < 0) {
-                    throw Error("pos < 0: "+source.pos)
-                }
-
-                return {
-                    buf: bbuf,
-                    err: null
-                };
-            } catch (e) {
-                return {
-                    buf: null,
-                    err: e.toString()
-                }
+            if (l < 0) {
+                serial.println("l < 0: "+l)
+                throw Error("l < 0: "+l)
             }
+
+//            serial.println(`readFull(${length} -> ${l}); pos: ${source.pos}`)
+
+            if (source.pos + l < 0) {
+                throw Error("pos < 0: "+source.pos)
+            }
+
+            source.pos += l;
+            return source.buf.readByteNumbers(l)
         };
 
         source.getPos = function () {
@@ -99,69 +88,39 @@ var Mp3 = {
         };
 
         source.skipTags = function () {
-            var result = source.readFull(3);
-            if (result.err) {
-                return {
-                    err: result.err
-                }
-            }
-            var buf = result.buf;
+            var t = source.buf.readStr(3);
+
+//            var buf = result.buf;
 
             // decode UTF-8
-            var t = String.fromCharCode.apply(null, buf);
             switch (t) {
                 case "TAG":
-                    result = source.readFull(125);
-                    if (result.err) {
-                        return {
-                            err: result.err
-                        }
-                    }
-                    buf = result.buf;
+                    source.readFull(125);
                     break;
                 case 'ID3':
                     // Skip version (2 bytes) and flag (1 byte)
-                    result = source.readFull(3);
-                    if (result.err) {
-                        return {
-                            err: result.err
-                        }
-                    }
+                    source.readFull(3);
 
-                    result = source.readFull(4);
-                    if (result.err) {
-                        return {
-                            err: result.err
-                        }
-                    }
-                    buf = result.buf;
-                    if (buf.byteLength !== 4) {
+                    let buf = source.readFull(4)
+                    if (buf.length !== 4) {
                         return {
                             err: "data not enough."
                         };
                     }
                     var size = (((buf[0] >>> 0) << 21) >>> 0) | (((buf[1] >>> 0) << 14) >>> 0) | (((buf[2] >>> 0) << 7) >>> 0) | (buf[3] >>> 0);
-                    result = source.readFull(size);
-                    if (result.err) {
-                        return {
-                            err: result.err
-                        }
-                    }
-                    buf = result.buf;
+
+                    source.readFull(size)
                     break;
                 default:
-                    source.unread(buf);
+                    source.buf.unread(3);
 //                    source.pos -= 3;
                     break;
             }
             return {};
         };
 
-        source.unread = function (buf) {
-            source.pos -= buf.byteLength
-        };
-
         source.rewind = function() {
+            source.buf.rewind()
             source.pos = 0;
         };
 
@@ -197,6 +156,9 @@ var Mp3 = {
 
         decoder.decode = function (callback) {
             var result;
+
+            serial.println("Start decoding")
+
             while(true) {
                 result = decoder.readFrame();
 
@@ -227,6 +189,9 @@ var Mp3 = {
 
             var l = 0;
             while(true) {
+
+//                serial.println(`Reading Frames; l = ${l}`)
+
                 var result = Frameheader.read(decoder.source, decoder.source.pos);
                 if (result.err) {
                     if (result.err.toString().indexOf("UnexpectedEOF") > -1) {
@@ -236,10 +201,12 @@ var Mp3 = {
                         err: result.err
                     };
                 }
+
+
                 decoder.frameStarts.push(result.position);
                 l += consts.BytesPerFrame;
 
-                result = decoder.source.readFull(result.h.frameSize() - 4); // move to next frame position
+                result = decoder.source.readFull(result.h.frameSize() - 4)[0]; // move to next frame position
                 if (result.err) {
                     break;
                 }
@@ -255,21 +222,31 @@ var Mp3 = {
         };
         // ======= Methods of decoder :: end =========
 
+//        serial.println("Reading tags")
+
         var r = s.skipTags();
         if (r && r.err) {
             throw Error(`Error creating new MP3 source: ${r.err}`)
             return null;
         }
 
+//        serial.println("Reading first frame")
+
         var result = decoder.readFrame();
         if (result.err) {
             throw Error(`Error reading frame: ${result.err}`)
             return null;
         }
 
+//        serial.println("First frame finished reading")
+
         decoder.sampleRate = decoder.frame.samplingFrequency();
 
+        serial.println("Sampling rate: "+decoder.sampleRate + " Hz")
+
         result = decoder.ensureFrameStartsAndLength();
+
+        serial.println("Decode end")
         if (result.err) {
             throw Error(`Error ensuring Frame starts and length: ${result.err}`)
             return null;