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Fix issue in Layer3.js where last frame is dropped
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Merge of open pull request in parent project audiocogs/mp3.js#19
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@Thalhammer
Thalhammer committed Sep 24, 2019
1 parent f900eed commit c242d3e
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Showing 3 changed files with 71 additions and 47 deletions.
14 changes: 6 additions & 8 deletions src/demuxer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -14,30 +14,28 @@ export class MP3Demuxer extends AV.Demuxer {
private sentInfo: boolean;

static probe(stream: AV.Stream) {
var off = stream.offset;
let off = stream.offset;

// skip id3 metadata if it exists
var id3header = MP3Demuxer.getID3v2Header(stream);
let id3header = MP3Demuxer.getID3v2Header(stream);
if (id3header)
stream.advance(10 + id3header.length);

// attempt to read the header of the first audio frame
var s = new MP3Stream(new AV.Bitstream(stream));
var header = null;
let s = new MP3Stream(new AV.Bitstream(stream));
let header = null;

try {
header = MP3FrameHeader.decode(s);
} catch (e) {
console.log(e);
};
} catch (e) {};

// go back to the beginning, for other probes
stream.seek(off);

return !!header;
}

static getID3v2Header(stream) :{
static getID3v2Header(stream) : {
version: string;
major: number;
minor: number;
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69 changes: 40 additions & 29 deletions src/layer3.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -90,17 +90,23 @@ export class Layer3 {

// find main_data of next frame
var peek = stream.copy();
peek.seek(stream.next_frame * 8);

var nextHeader = peek.read(16);
if ((nextHeader & 0xffe6) === 0xffe2) { // syncword | layer
if ((nextHeader & 1) === 0) // protection bit
peek.advance(16); // crc check

peek.advance(16); // skip the rest of the header
next_md_begin = peek.read((nextHeader & 8) ? 9 : 8);
var nextHeader = null;
try {
peek.seek(stream.next_frame * 8);
nextHeader = peek.read(16);
if ((nextHeader & 0xffe6) === 0xffe2) { // syncword | layer
if ((nextHeader & 1) === 0) // protection bit
peek.advance(16); // crc check

peek.advance(16); // skip the rest of the header
next_md_begin = peek.read((nextHeader & 8) ? 9 : 8);
}
} catch (err) {
if (err instanceof AV.UnderflowError) {
next_md_begin = 0;
nextHeader = null;
} else throw err;
}

// find main_data of this frame
var frame_space = stream.next_frame - stream.nextByte();

Expand Down Expand Up @@ -141,26 +147,31 @@ export class Layer3 {
// decode main_data
this.decodeMainData(ptr, frame, si, nch);

// preload main_data buffer with up to 511 bytes for next frame(s)
if (frame_free >= next_md_begin) {
this.memcpy(stream.main_data, 0, stream.stream.stream, stream.next_frame - next_md_begin, next_md_begin);
stream.md_len = next_md_begin;
} else {
if (md_len < si.main_data_begin) {
var extra = si.main_data_begin - md_len;
if (extra + frame_free > next_md_begin)
extra = next_md_begin - frame_free;

if (extra < stream.md_len) {
this.memcpy(stream.main_data, 0, stream.main_data, stream.md_len - extra, extra);
stream.md_len = extra;
}
if (next_md_begin > 0) {
// preload main_data buffer with up to 511 bytes for next frame(s)
if (frame_free >= next_md_begin) {
this.memcpy(stream.main_data, 0, stream.stream.stream, stream.next_frame - next_md_begin, next_md_begin);
stream.md_len = next_md_begin;
} else {
stream.md_len = 0;
}
if (md_len < si.main_data_begin) {
var extra = si.main_data_begin - md_len;
if (extra + frame_free > next_md_begin)
extra = next_md_begin - frame_free;

if (extra < stream.md_len) {
this.memcpy(stream.main_data, 0, stream.main_data, stream.md_len - extra, extra);
stream.md_len = extra;
}
} else {
stream.md_len = 0;
}

this.memcpy(stream.main_data, stream.md_len, stream.stream.stream, stream.next_frame - frame_free, frame_free);
stream.md_len += frame_free;
this.memcpy(stream.main_data, stream.md_len, stream.stream.stream, stream.next_frame - frame_free, frame_free);
stream.md_len += frame_free;
}
} else {
stream.md_len = 0;
stream.main_data.fill(0);
}
}

Expand Down Expand Up @@ -1017,7 +1028,7 @@ export class Layer3 {
if (!(modes[sfbi] & tables.I_STEREO))
continue;

let is_pos = right_ch.scalefac[sfbi];
let is_pos = right_ch.scalefac[sfbi];

if (is_pos >= 7) { // illegal intensity position
modes[sfbi] &= ~tables.I_STEREO;
Expand Down
35 changes: 25 additions & 10 deletions src/stream.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,13 @@ import {MP3FrameHeader} from './header';

export class MP3Stream {
private stream: AV.Bitstream; // actual bitstream
private sync; // stream sync found
private freerate; // free bitrate (fixed)
private this_frame; // start of current frame
private next_frame; // start of next frame
private sync: boolean; // stream sync found
private freerate: number; // free bitrate (fixed)
private this_frame: number; // start of current frame
private next_frame: number; // start of next frame

private main_data; // actual audio data
private md_len; // length of main data
private main_data: Uint8Array; // actual audio data
private md_len: number; // length of main data


constructor(stream: AV.Bitstream) {
Expand Down Expand Up @@ -39,12 +39,27 @@ export class MP3Stream {
getU8(offset) {
var stream = this.stream.stream;
return stream.peekUInt8(offset - stream.offset);
};
}

getU16(offset) {
var stream = this.stream.stream;
return stream.peekUInt16(offset - stream.offset);
}

getU24(offset) {
var stream = this.stream.stream;
return stream.peekUInt24(offset - stream.offset);
}

getU32(offset) {
var stream = this.stream.stream;
return stream.peekUInt32(offset - stream.offset);
}

nextByte() {
var stream = this.stream;
return stream.bitPosition === 0 ? stream.stream.offset : stream.stream.offset + 1;
};
}

doSync() {
var stream = this.stream.stream;
Expand All @@ -58,11 +73,11 @@ export class MP3Stream {
return false;

return true;
};
}

reset(byteOffset) {
this.stream.seek(byteOffset * 8);
this.next_frame = byteOffset;
this.sync = true;
};
}
}

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