From c4aaeef6b1f1ababff65d7465f993c36572acfcf Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Tue, 17 Jan 2017 11:26:51 +0200
Subject: [PATCH] Removed homebrew MP3 format detection

It didn't work for all files so let libmpg123 handle all quirks for us
See https://mantis.zdoom.org/view.php?id=60
---
 src/sound/mpg123_decoder.cpp | 51 ++++--------------------------------
 src/sound/mpg123_decoder.h   |  1 -
 2 files changed, 5 insertions(+), 47 deletions(-)

diff --git a/src/sound/mpg123_decoder.cpp b/src/sound/mpg123_decoder.cpp
index 9d1fff97ec..0a2ba94f1b 100644
--- a/src/sound/mpg123_decoder.cpp
+++ b/src/sound/mpg123_decoder.cpp
@@ -14,25 +14,22 @@ static bool inited = false;
 
 off_t MPG123Decoder::file_lseek(void *handle, off_t offset, int whence)
 {
-    MPG123Decoder *self = reinterpret_cast<MPG123Decoder*>(handle);
-    FileReader *reader = self->Reader;
+    FileReader *reader = reinterpret_cast<MPG123Decoder*>(handle)->Reader;
 
-    if(whence == SEEK_SET)
-        offset += self->StartOffset;
-    else if(whence == SEEK_CUR)
+    if(whence == SEEK_CUR)
     {
-        if(offset < 0 && reader->Tell()+offset < self->StartOffset)
+        if(offset < 0 && reader->Tell()+offset < 0)
             return -1;
     }
     else if(whence == SEEK_END)
     {
-        if(offset < 0 && reader->GetLength()+offset < self->StartOffset)
+        if(offset < 0 && reader->GetLength()+offset < 0)
             return -1;
     }
 
     if(reader->Seek(offset, whence) != 0)
         return -1;
-    return reader->Tell() - self->StartOffset;
+    return reader->Tell();
 }
 
 ssize_t MPG123Decoder::file_read(void *handle, void *buffer, size_t bytes)
@@ -71,45 +68,7 @@ bool MPG123Decoder::open(FileReader *reader)
     }
 
     Reader = reader;
-    StartOffset = 0;
 
-    char data[10];
-    if(file_read(this, data, 10) != 10)
-        return false;
-
-    int start_offset = 0;
-    // Check for ID3 tags and skip them
-    if(memcmp(data, "ID3", 3) == 0 &&
-       (BYTE)data[3] <= 4 && (BYTE)data[4] != 0xff &&
-       (data[5]&0x0f) == 0 && (data[6]&0x80) == 0 &&
-       (data[7]&0x80) == 0 && (data[8]&0x80) == 0 &&
-       (data[9]&0x80) == 0)
-    {
-        // ID3v2
-        start_offset  = (data[6]<<21) | (data[7]<<14) |
-                        (data[8]<< 7) | (data[9]    );
-        start_offset += ((data[5]&0x10) ? 20 : 10);
-    }
-
-    StartOffset = start_offset;
-    if(file_lseek(this, 0, SEEK_SET) != 0)
-        return false;
-
-    // Check for a frame header
-    bool frame_ok = false;
-    if(file_read(this, data, 3) == 3)
-    {
-        if((BYTE)data[0] == 0xff &&
-           ((data[1]&0xfe) == 0xfa/*MPEG-1*/ || (data[1]&0xfe) == 0xf2/*MPEG-2*/))
-        {
-            int brate_idx = (data[2]>>4) & 0x0f;
-            int srate_idx = (data[2]>>2) & 0x03;
-            if(brate_idx != 0 && brate_idx != 15 && srate_idx != 3)
-                frame_ok = (file_lseek(this, 0, SEEK_SET) == 0);
-        }
-    }
-
-    if(frame_ok)
     {
         MPG123 = mpg123_new(NULL, NULL);
         if(mpg123_replace_reader_handle(MPG123, file_read, file_lseek, NULL) == MPG123_OK &&
diff --git a/src/sound/mpg123_decoder.h b/src/sound/mpg123_decoder.h
index 1d5b883ead..051473abb1 100644
--- a/src/sound/mpg123_decoder.h
+++ b/src/sound/mpg123_decoder.h
@@ -30,7 +30,6 @@ private:
     bool Done;
 
     FileReader *Reader;
-    int StartOffset;
     static off_t file_lseek(void *handle, off_t offset, int whence);
     static ssize_t file_read(void *handle, void *buffer, size_t bytes);