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Remove OffsetFix

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Mimic BASS decoding peculiarities
This commit is contained in:
Glenn Maynard
2004-01-24 20:00:41 +00:00
parent 268bff458d
commit 47530d2117
2 changed files with 47 additions and 117 deletions
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stepmania/src/RageSoundReader_MP3.cpp
+47 -114
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@@ -148,6 +148,7 @@ struct xing
unsigned long bytes; /* total number of bytes */
unsigned char toc[100]; /* 100-point seek table */
long scale; /* ?? */
enum { XING, INFO } type;
};
enum {
@@ -295,7 +296,24 @@ int RageSoundReader_MP3::handle_first_frame()
int bytes = mad->filesize - mad->header_bytes;
mad->bitrate = (int)(bytes * 8 / (mad->length/1000.f));
ret = 1;
/* "Info" tags are written by some tools: LAME in CBR, Fb2k. They're just
* Xing tags. I suspect LAME does this to avoid confsing decoders that
* assume files with Xing tags are VBR.
*
* However, DWI's decoder, BASS, doesn't understand this, and treats it as
* a corrupt frame, outputting a frame of silence.
*
* I can't quite decide. We can decode correctly, which means sync won't change
* if a Xing tag is rewritten to an Info tag (eg. "Fix MP3 headers..." in FB2k.)
*
* However, that'll result in different sync than DWI.
*
* Let's be compatible with DWI in this; different sync is annoying, and most
* people probably aren't changing header types. However, decode the header
* anyway, so we can use the data in it.
*/
if( mad->xingtag.type == xing::XING )
ret = 1;
}
/* If there's no Xing tag, mad->length will be filled in by _open. */
@@ -365,6 +383,22 @@ int RageSoundReader_MP3::do_mad_frame_decode( bool headers_only )
ret=mad_header_decode( &mad->Frame.header,&mad->Stream );
else
ret=mad_frame_decode( &mad->Frame,&mad->Stream );
if( mad->Stream.error == MAD_ERROR_BADDATAPTR && mad->first_frame )
{
/*
* Something's corrupt. One cause of this is cutting an MP3 in the middle
* without reencoding; the first two frames will reference data from previous
* frames that have been removed. The frame is valid--we can get a header from
* it, we just can't synth useful data.
*
* BASS pretends the bad frame is silent. Let's emulate that if we're at the
* beginning, since that's probably a cut. The only time I've seen this in
* the middle of a stream is a corruption, which will probably lose sync anyway.
*/
ret = 0; /* pretend success */
}
if( !ret )
{
/* OK. */
@@ -449,112 +483,6 @@ int RageSoundReader_MP3::do_mad_frame_decode( bool headers_only )
}
}
/* Previously, there was a bug in MADLIB_rewind: it didn't clear synth. This
* resulted in some files having a few frames of silence at the beginning, throwing
* off sync. Figure out how far ahead the file was offset under those conditions,
* so we can emulate that sync offset. */
int RageSoundReader_MP3::FindOffsetFix()
{
/* Do a fake rewind. */
file.Rewind();
mad_frame_mute(&mad->Frame);
mad_synth_mute(&mad->Synth);
mad_timer_reset(&mad->Timer);
mad->outpos = mad->outleft = 0;
// mad_stream_finish(&mad->Stream); // fake
// mad_stream_init(&mad->Stream); // fake
mad_stream_buffer(&mad->Stream, NULL, 0);
mad->inbuf_filepos = 0;
mad->header_bytes = 0;
mad->first_frame = true;
/* Read a couple frames, to make sure we're synced. */
int FramesToRead = 5;
while( FramesToRead-- )
{
int ret = do_mad_frame_decode();
if( ret == 0 )
{
SetError("Unexpected EOF");
return false;
}
if( ret == -1 )
return false; /* it set the error */
/* If this frame is silent, it's not an appropriate sample. Find
* a frame with actual sound in it. */
if( !FramesToRead )
{
/* We've read enough frames. Now, make sure this frame isn't silent. */
bool Silent = true;
for( int j = 0; j < 2; ++j )
for( int k = 0; k < 36; ++k )
for( int l = 0; l < 32; ++l )
if( mad->Frame.sbsample[j][k][l] )
Silent=false;
/* If it's silent, it's not an appropriate sample. Find a frame
* with actual sound in it. */
if( Silent )
++FramesToRead;
}
}
/* Clear the TOC cache. We might have cached bogus values. */
int i;
for( i = 0; i < 200; ++i)
mad->toc[i] = -1;
/* Save the current timestamp. This is the time we thought we were at when
* we decoded the last frame. */
mad_timer_t Apparent = mad->Timer;
/* Save the last frame's subband samples. */
mad_fixed_t cpy[2][36][32];
memcpy( cpy, mad->Frame.sbsample, sizeof(mad->Frame.sbsample) );
/* Do a real rewind. */
MADLIB_rewind();
/* Search for the frame we just saved. */
mad_timer_t Actual = mad_timer_zero;
bool found = false;
for( i = 0; i < 10; ++i )
{
int ret = do_mad_frame_decode();
if( ret == 0 )
{
SetError("Unexpected EOF");
return false;
}
if( ret == -1 )
return false; /* it set the error */
if( !memcmp( cpy, mad->Frame.sbsample, sizeof(mad->Frame.sbsample) ) )
{
/* Found it. Record that frame's real timestamp. */
Actual = mad->Timer;
found = true;
break;
}
}
if( found )
{
/* Save the offset, so timestamps can be corrected. */
mad_timer_t Offset = Apparent;
mad_timer_sub( &Offset, Actual );
this->OffsetFix = mad_timer_count( Offset, (mad_units) 1000) / 1000.0f;
}
else
this->OffsetFix = 0;
MADLIB_rewind();
return true;
}
void RageSoundReader_MP3::synth_output()
{
@@ -726,10 +654,6 @@ SoundReader_FileReader::OpenResult RageSoundReader_MP3::Open( CString filename_
* the stream. */
synth_output();
// ret = FindOffsetFix();
// ASSERT( ret != -1 );
this->OffsetFix = 0;
if(mad->length == -1)
{
/* If vbr and !xing, this is just an estimate. */
@@ -755,7 +679,6 @@ SoundReader *RageSoundReader_MP3::Copy() const
ret->SampleRate = SampleRate;
ret->mad->framelength = mad->framelength;
ret->Channels = Channels;
ret->OffsetFix = OffsetFix;
ret->mad->length = mad->length;
// int n = ret->do_mad_frame_decode();
@@ -1145,8 +1068,18 @@ void xing_init(struct xing *xing)
int xing_parse(struct xing *xing, struct mad_bitptr ptr, unsigned int bitlen)
{
const unsigned XING_MAGIC = (('X' << 24) | ('i' << 16) | ('n' << 8) | 'g');
if (bitlen < 64 || mad_bit_read(&ptr, 32) != XING_MAGIC)
goto fail;
const unsigned INFO_MAGIC = (('I' << 24) | ('n' << 16) | ('f' << 8) | 'o');
unsigned data;
if (bitlen < 64)
goto fail;
data = mad_bit_read(&ptr, 32);
if( data == XING_MAGIC )
xing->type = xing::XING;
else if( data == INFO_MAGIC )
xing->type = xing::INFO;
else
goto fail;
xing->flags = mad_bit_read(&ptr, 32);
bitlen -= 64;