ref: 8f26e5a1c1e30bb75616ebc31a1a994a508c74dc
dir: /src/info.c/
/********************************************************************
* *
* THIS FILE IS PART OF THE libopusfile SOFTWARE CODEC SOURCE CODE. *
* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
* *
* THE libopusfile SOURCE CODE IS (C) COPYRIGHT 2012 *
* by the Xiph.Org Foundation and contributors http://www.xiph.org/ *
* *
********************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "internal.h"
#include <limits.h>
#include <string.h>
static unsigned op_parse_uint16le(const unsigned char *_data){
return _data[0]|_data[1]<<8;
}
static int op_parse_int16le(const unsigned char *_data){
int ret;
ret=_data[0]|_data[1]<<8;
return (ret^0x8000)-0x8000;
}
static opus_uint32 op_parse_uint32le(const unsigned char *_data){
return _data[0]|_data[1]<<8|_data[2]<<16|_data[3]<<24;
}
static opus_uint32 op_parse_uint32be(const unsigned char *_data){
return _data[3]|_data[2]<<8|_data[1]<<16|_data[0]<<24;
}
int opus_head_parse(OpusHead *_head,const unsigned char *_data,size_t _len){
OpusHead head;
if(_len<8)return OP_ENOTFORMAT;
if(memcmp(_data,"OpusHead",8)!=0)return OP_ENOTFORMAT;
if(_len<9)return OP_EBADHEADER;
head.version=_data[8];
if(head.version>15)return OP_EVERSION;
if(_len<19)return OP_EBADHEADER;
head.channel_count=_data[9];
head.pre_skip=op_parse_uint16le(_data+10);
head.input_sample_rate=op_parse_uint32le(_data+12);
head.output_gain=op_parse_int16le(_data+16);
head.mapping_family=_data[18];
if(head.mapping_family==0){
if(head.channel_count<1||head.channel_count>2)return OP_EBADHEADER;
if(head.version<=1&&_len>19)return OP_EBADHEADER;
head.stream_count=1;
head.coupled_count=head.channel_count-1;
if(_head!=NULL){
_head->mapping[0]=0;
_head->mapping[1]=1;
}
}
else if(head.mapping_family==1){
size_t size;
int ci;
if(head.channel_count<1||head.channel_count>8)return OP_EBADHEADER;
size=21+head.channel_count;
if(_len<size||head.version<=1&&_len>size)return OP_EBADHEADER;
head.stream_count=_data[19];
if(head.stream_count<1)return OP_EBADHEADER;
head.coupled_count=_data[20];
if(head.coupled_count>head.stream_count)return OP_EBADHEADER;
for(ci=0;ci<head.channel_count;ci++){
if(_data[21+ci]>=head.stream_count+head.coupled_count
&&_data[21+ci]!=255){
return OP_EBADHEADER;
}
}
if(_head!=NULL)memcpy(_head->mapping,_data+21,head.channel_count);
}
/*General purpose players should not attempt to play back content with
channel mapping family 255.*/
else if(head.mapping_family==255)return OP_EIMPL;
/*No other channel mapping families are currently defined.*/
else return OP_EBADHEADER;
if(_head!=NULL)memcpy(_head,&head,head.mapping-(unsigned char *)&head);
return 0;
}
void opus_tags_init(OpusTags *_tags){
memset(_tags,0,sizeof(*_tags));
}
void opus_tags_clear(OpusTags *_tags){
int i;
for(i=_tags->comments;i-->0;)_ogg_free(_tags->user_comments[i]);
_ogg_free(_tags->user_comments);
_ogg_free(_tags->comment_lengths);
_ogg_free(_tags->vendor);
}
/*The actual implementation of opus_tags_parse().
Unlike the public API, this function requires _tags to already be
initialized, modifies its contents before success is guaranteed, and assumes
the caller will clear it on error.*/
int opus_tags_parse_impl(OpusTags *_tags,
const unsigned char *_data,size_t _len){
opus_uint32 count;
size_t size;
size_t len;
int ncomments;
int i;
len=_len;
if(len<8)return OP_ENOTFORMAT;
if(memcmp(_data,"OpusTags",8)!=0)return OP_ENOTFORMAT;
if(len<16)return OP_EBADHEADER;
_data+=8;
len-=8;
count=op_parse_uint32le(_data);
_data+=4;
len-=4;
if(count>len)return OP_EBADHEADER;
if(_tags!=NULL){
char *vendor;
size=count+1;
if(size<count)return OP_EFAULT;
vendor=(char *)_ogg_malloc(size);
if(vendor==NULL)return OP_EFAULT;
memcpy(vendor,_data,count);
vendor[count]='\0';
_tags->vendor=vendor;
}
_data+=count;
len-=count;
if(len<4)return OP_EBADHEADER;
count=op_parse_uint32le(_data);
_data+=4;
len-=4;
/*Check to make sure there's minimally sufficient data left in the packet.*/
if(count>len>>2)return OP_EBADHEADER;
/*Check for overflow (the API limits this to an int).*/
if(count>(opus_uint32)INT_MAX-1)return OP_EFAULT;
if(_tags!=NULL){
size=sizeof(*_tags->comment_lengths)*(count+1);
if(size/sizeof(*_tags->comment_lengths)!=count+1)return OP_EFAULT;
_tags->comment_lengths=(int *)_ogg_malloc(size);
size=sizeof(*_tags->user_comments)*(count+1);
if(size/sizeof(*_tags->user_comments)!=count+1)return OP_EFAULT;
_tags->user_comments=(char **)_ogg_malloc(size);
if(_tags->comment_lengths==NULL||_tags->user_comments==NULL){
return OP_EFAULT;
}
}
ncomments=(int)count;
for(i=0;i<ncomments;i++){
/*Check to make sure there's minimally sufficient data left in the packet.*/
if((size_t)(ncomments-i)>len>>2)return OP_EBADHEADER;
count=op_parse_uint32le(_data);
_data+=4;
len-=4;
if(count>len)return OP_EBADHEADER;
/*Check for overflow (the API limits this to an int).*/
if(count>(opus_uint32)INT_MAX)return OP_EFAULT;
if(_tags!=NULL){
_tags->comment_lengths[i]=(int)count;
size=count+1;
if(size<count)return OP_EFAULT;
_tags->user_comments[i]=(char *)_ogg_malloc(size);
if(_tags->user_comments[i]==NULL)return OP_EFAULT;
_tags->comments=i+1;
memcpy(_tags->user_comments[i],_data,count);
_tags->user_comments[i][count]='\0';
}
_data+=count;
len-=count;
}
if(_tags!=NULL){
_tags->user_comments[ncomments]=NULL;
_tags->comment_lengths[ncomments]=0;
}
return 0;
}
int opus_tags_parse(OpusTags *_tags,const unsigned char *_data,size_t _len){
if(_tags!=NULL){
OpusTags tags;
int ret;
opus_tags_init(&tags);
ret=opus_tags_parse_impl(&tags,_data,_len);
if(ret<0)opus_tags_clear(&tags);
else *_tags=*&tags;
return ret;
}
else return opus_tags_parse_impl(NULL,_data,_len);
}
/*Add room for a new comment.*/
static int op_tags_add_prepare(OpusTags *_tags){
char **user_comments;
int *comment_lengths;
int ncomments;
ncomments=_tags->comments;
user_comments=(char **)_ogg_realloc(_tags->user_comments,
sizeof(*_tags->user_comments)*(ncomments+2));
if(OP_UNLIKELY(user_comments==NULL))return OP_EFAULT;
_tags->user_comments=user_comments;
comment_lengths=(int *)_ogg_realloc(_tags->comment_lengths,
sizeof(*_tags->comment_lengths)*(ncomments+2));
if(OP_UNLIKELY(comment_lengths==NULL))return OP_EFAULT;
_tags->comment_lengths=comment_lengths;
comment_lengths[ncomments]=comment_lengths[ncomments+1]=0;
/*Our caller will always set user_comments[ncomments].*/
user_comments[ncomments+1]=NULL;
return 0;
}
int opus_tags_add(OpusTags *_tags,const char *_tag,const char *_value){
char *comment;
int tag_len;
int value_len;
int ncomments;
int ret;
ret=op_tags_add_prepare(_tags);
if(OP_UNLIKELY(ret<0))return ret;
tag_len=strlen(_tag);
value_len=strlen(_value);
ncomments=_tags->comments;
/*+2 for '=' and '\0'.*/
_tags->user_comments[ncomments]=comment=
(char *)_ogg_malloc(sizeof(*comment)*(tag_len+value_len+2));
if(OP_UNLIKELY(comment==NULL))return OP_EFAULT;
_tags->comment_lengths[ncomments]=tag_len+value_len+1;
memcpy(comment,_tag,sizeof(*comment)*tag_len);
comment[tag_len]='=';
memcpy(comment+tag_len+1,_value,sizeof(*comment)*(value_len+1));
return 0;
}
int opus_tags_add_comment(OpusTags *_tags,const char *_comment){
char *comment;
int ncomments;
int comment_len;
int ret;
ret=op_tags_add_prepare(_tags);
if(OP_UNLIKELY(ret<0))return ret;
comment_len=strlen(_comment);
ncomments=_tags->comments;
_tags->user_comments[ncomments]=comment=(char *)
_ogg_malloc(sizeof(*_tags->user_comments[ncomments])*(comment_len+1));
if(OP_UNLIKELY(comment==NULL))return OP_EFAULT;
_tags->comment_lengths[ncomments]=comment_len;
memcpy(comment,_comment,sizeof(*comment)*(comment_len+1));
return 0;
}
/*Is _a a "tag=value" comment whose tag matches _b?
0 if it is, a non-zero value otherwise.*/
static int op_tagcompare(const char *_a,const char *_b,int _n){
return op_strncasecmp(_a,_b,_n)||_a[_n]!='=';
}
const char *opus_tags_query(const OpusTags *_tags,const char *_tag,int _count){
char **user_comments;
int tag_len;
int found;
int ncomments;
int ci;
tag_len=strlen(_tag);
ncomments=_tags->comments;
user_comments=_tags->user_comments;
found=0;
for(ci=0;ci<ncomments;ci++){
if(!op_tagcompare(user_comments[ci],_tag,tag_len)){
/*We return a pointer to the data, not a copy.*/
if(_count==found++)return user_comments[ci]+tag_len+1;
}
}
/*Didn't find anything.*/
return NULL;
}
int opus_tags_query_count(const OpusTags *_tags,const char *_tag){
char **user_comments;
int tag_len;
int found;
int ncomments;
int ci;
tag_len=strlen(_tag);
ncomments=_tags->comments;
user_comments=_tags->user_comments;
found=0;
for(ci=0;ci<ncomments;ci++){
if(!op_tagcompare(user_comments[ci],_tag,tag_len))found++;
}
return found;
}
int opus_tags_get_track_gain(const OpusTags *_tags,int *_gain_q8){
char **comments;
int *comment_lengths;
int ncomments;
int ci;
comments=_tags->user_comments;
comment_lengths=_tags->comment_lengths;
ncomments=_tags->comments;
/*Look for the first valid R128_TRACK_GAIN tag and use that.*/
for(ci=0;ci<ncomments;ci++){
if(comment_lengths[ci]>16
&&op_strncasecmp(comments[ci],"R128_TRACK_GAIN=",16)==0){
char *p;
opus_int32 gain_q8;
int negative;
p=comments[ci]+16;
negative=0;
if(*p=='-'){
negative=-1;
p++;
}
else if(*p=='+')p++;
gain_q8=0;
while(*p>='0'&&*p<='9'){
gain_q8=10*gain_q8+*p-'0';
if(gain_q8>32767-negative)break;
p++;
}
/*This didn't look like a signed 16-bit decimal integer.
Not a valid R128_TRACK_GAIN tag.*/
if(*p!='\0')continue;
*_gain_q8=(int)(gain_q8+negative^negative);
return 0;
}
}
return OP_FALSE;
}
static int op_is_jpeg(const unsigned char *_buf,size_t _buf_sz){
return _buf_sz>=11&&memcmp(_buf,"\xFF\xD8\xFF\xE0",4)==0
&&(_buf[4]<<8|_buf[5])>=16&&memcmp(_buf+6,"JFIF",5)==0;
}
/*Tries to extract the width, height, bits per pixel, and palette size of a
JPEG.
On failure, simply leaves its outputs unmodified.*/
static void op_extract_jpeg_params(const unsigned char *_buf,size_t _buf_sz,
opus_uint32 *_width,opus_uint32 *_height,
opus_uint32 *_depth,opus_uint32 *_colors,int *_has_palette){
if(op_is_jpeg(_buf,_buf_sz)){
size_t offs;
offs=2;
for(;;){
size_t segment_len;
int marker;
while(offs<_buf_sz&&_buf[offs]!=0xFF)offs++;
while(offs<_buf_sz&&_buf[offs]==0xFF)offs++;
marker=_buf[offs];
offs++;
/*If we hit EOI* (end of image), or another SOI* (start of image),
or SOS (start of scan), then stop now.*/
if(offs>=_buf_sz||(marker>=0xD8&&marker<=0xDA))break;
/*RST* (restart markers): skip (no segment length).*/
else if(marker>=0xD0&&marker<=0xD7)continue;
/*Read the length of the marker segment.*/
if(_buf_sz-offs<2)break;
segment_len=_buf[offs]<<8|_buf[offs+1];
if(segment_len<2||_buf_sz-offs<segment_len)break;
if(marker==0xC0||(marker>0xC0&&marker<0xD0&&(marker&3)!=0)){
/*Found a SOFn (start of frame) marker segment:*/
if(segment_len>=8){
*_height=_buf[offs+3]<<8|_buf[offs+4];
*_width=_buf[offs+5]<<8|_buf[offs+6];
*_depth=_buf[offs+2]*_buf[offs+7];
*_colors=0;
*_has_palette=0;
}
break;
}
/*Other markers: skip the whole marker segment.*/
offs+=segment_len;
}
}
}
static int op_is_png(const unsigned char *_buf,size_t _buf_sz){
return _buf_sz>=8&&memcmp(_buf,"\x89PNG\x0D\x0A\x1A\x0A",8)==0;
}
/*Tries to extract the width, height, bits per pixel, and palette size of a
PNG.
On failure, simply leaves its outputs unmodified.*/
static void op_extract_png_params(const unsigned char *_buf,size_t _buf_sz,
opus_uint32 *_width,opus_uint32 *_height,
opus_uint32 *_depth,opus_uint32 *_colors,int *_has_palette){
if(op_is_png(_buf,_buf_sz)){
size_t offs;
offs=8;
while(_buf_sz-offs>=12){
ogg_uint32_t chunk_len;
chunk_len=op_parse_uint32be(_buf+offs);
if(chunk_len>_buf_sz-(offs+12))break;
else if(chunk_len==13&&memcmp(_buf+offs+4,"IHDR",4)==0){
int color_type;
*_width=op_parse_uint32be(_buf+offs+8);
*_height=op_parse_uint32be(_buf+offs+12);
color_type=_buf[offs+17];
if(color_type==3){
*_depth=24;
*_has_palette=1;
}
else{
int sample_depth;
sample_depth=_buf[offs+16];
if(color_type==0)*_depth=sample_depth;
else if(color_type==2)*_depth=sample_depth*3;
else if(color_type==4)*_depth=sample_depth*2;
else if(color_type==6)*_depth=sample_depth*4;
*_colors=0;
*_has_palette=0;
break;
}
}
else if(*_has_palette>0&&memcmp(_buf+offs+4,"PLTE",4)==0){
*_colors=chunk_len/3;
break;
}
offs+=12+chunk_len;
}
}
}
static int op_is_gif(const unsigned char *_buf,size_t _buf_sz){
return _buf_sz>=6&&(memcmp(_buf,"GIF87a",6)==0||memcmp(_buf,"GIF89a",6)==0);
}
/*Tries to extract the width, height, bits per pixel, and palette size of a
GIF.
On failure, simply leaves its outputs unmodified.*/
static void op_extract_gif_params(const unsigned char *_buf,size_t _buf_sz,
opus_uint32 *_width,opus_uint32 *_height,
opus_uint32 *_depth,opus_uint32 *_colors,int *_has_palette){
if(op_is_gif(_buf,_buf_sz)&&_buf_sz>=14){
*_width=_buf[6]|_buf[7]<<8;
*_height=_buf[8]|_buf[9]<<8;
/*libFLAC hard-codes the depth to 24.*/
*_depth=24;
*_colors=1<<((_buf[10]&7)+1);
*_has_palette=1;
}
}
/*The actual implementation of opus_picture_tag_parse().
Unlike the public API, this function requires _pic to already be
initialized, modifies its contents before success is guaranteed, and assumes
the caller will clear it on error.*/
static int opus_picture_tag_parse_impl(OpusPictureTag *_pic,const char *_tag,
unsigned char *_buf,size_t _buf_sz,size_t _base64_sz){
opus_int32 picture_type;
opus_uint32 mime_type_length;
char *mime_type;
opus_uint32 description_length;
char *description;
opus_uint32 width;
opus_uint32 height;
opus_uint32 depth;
opus_uint32 colors;
opus_uint32 data_length;
opus_uint32 file_width;
opus_uint32 file_height;
opus_uint32 file_depth;
opus_uint32 file_colors;
int format;
int has_palette;
int colors_set;
size_t i;
/*Decode the BASE64 data.*/
for(i=0;i<_base64_sz;i++){
opus_uint32 value;
int j;
value=0;
for(j=0;j<4;j++){
unsigned c;
unsigned d;
c=(unsigned char)_tag[4*i+j];
if(c=='+')d=62;
else if(c=='/')d=63;
else if(c>='0'&&c<='9')d=52+c-'0';
else if(c>='a'&&c<='z')d=26+c-'a';
else if(c>='A'&&c<='Z')d=c-'A';
else if(c=='='&&3*i+j>_buf_sz)d=0;
else return OP_ENOTFORMAT;
value=value<<6|d;
}
_buf[3*i]=(unsigned char)(value>>16);
if(3*i+1<_buf_sz){
_buf[3*i+1]=(unsigned char)(value>>8);
if(3*i+2<_buf_sz)_buf[3*i+2]=(unsigned char)value;
}
}
i=0;
picture_type=op_parse_uint32be(_buf+i);
i+=4;
/*Extract the MIME type.*/
mime_type_length=op_parse_uint32be(_buf+i);
i+=4;
if(mime_type_length>_buf_sz-32)return OP_ENOTFORMAT;
mime_type=(char *)_ogg_malloc(sizeof(*_pic->mime_type)*(mime_type_length+1));
if(mime_type==NULL)return OP_EFAULT;
memcpy(mime_type,_buf+i,sizeof(*mime_type)*mime_type_length);
mime_type[mime_type_length]='\0';
_pic->mime_type=mime_type;
i+=mime_type_length;
/*Extract the description string.*/
description_length=op_parse_uint32be(_buf+i);
i+=4;
if(description_length>_buf_sz-mime_type_length-32)return OP_ENOTFORMAT;
description=
(char *)_ogg_malloc(sizeof(*_pic->mime_type)*(description_length+1));
if(description==NULL)return OP_EFAULT;
memcpy(description,_buf+i,sizeof(*description)*description_length);
description[description_length]='\0';
_pic->description=description;
i+=description_length;
/*Extract the remaining fields.*/
width=op_parse_uint32be(_buf+i);
i+=4;
height=op_parse_uint32be(_buf+i);
i+=4;
depth=op_parse_uint32be(_buf+i);
i+=4;
colors=op_parse_uint32be(_buf+i);
i+=4;
/*If one of these is set, they all must be, but colors==0 is a valid value.*/
colors_set=width!=0||height!=0||depth!=0||colors!=0;
if(width==0||height==0||depth==0&&colors_set)return OP_ENOTFORMAT;
data_length=op_parse_uint32be(_buf+i);
i+=4;
if(data_length>_buf_sz-i)return OP_ENOTFORMAT;
/*Trim extraneous data so we don't copy it below.*/
_buf_sz=i+data_length;
/*Attempt to determine the image format.*/
format=OP_PIC_FORMAT_UNKNOWN;
if(mime_type_length==3&&strcmp(mime_type,"-->")==0){
format=OP_PIC_FORMAT_URL;
/*Picture type 1 must be a 32x32 PNG.*/
if(picture_type==1&&(width!=0||height!=0)&&(width!=32||height!=32)){
return OP_ENOTFORMAT;
}
/*Append a terminating NUL for the convenience of our callers.*/
_buf[_buf_sz++]='\0';
}
else{
if(mime_type_length==10
&&op_strncasecmp(mime_type,"image/jpeg",mime_type_length)==0){
if(op_is_jpeg(_buf+i,data_length))format=OP_PIC_FORMAT_JPEG;
}
else if(mime_type_length==9
&&op_strncasecmp(mime_type,"image/png",mime_type_length)==0){
if(op_is_png(_buf+i,data_length))format=OP_PIC_FORMAT_PNG;
}
else if(mime_type_length==9
&&op_strncasecmp(mime_type,"image/gif",mime_type_length)==0){
if(op_is_gif(_buf+i,data_length))format=OP_PIC_FORMAT_GIF;
}
else if(mime_type_length==0||(mime_type_length==6
&&op_strncasecmp(mime_type,"image/",mime_type_length)==0)){
if(op_is_jpeg(_buf+i,data_length))format=OP_PIC_FORMAT_JPEG;
else if(op_is_png(_buf+i,data_length))format=OP_PIC_FORMAT_PNG;
else if(op_is_gif(_buf+i,data_length))format=OP_PIC_FORMAT_GIF;
}
file_width=file_height=file_depth=file_colors=0;
has_palette=-1;
switch(format){
case OP_PIC_FORMAT_JPEG:{
op_extract_jpeg_params(_buf+i,data_length,
&file_width,&file_height,&file_depth,&file_colors,&has_palette);
}break;
case OP_PIC_FORMAT_PNG:{
op_extract_png_params(_buf+i,data_length,
&file_width,&file_height,&file_depth,&file_colors,&has_palette);
}break;
case OP_PIC_FORMAT_GIF:{
op_extract_gif_params(_buf+i,data_length,
&file_width,&file_height,&file_depth,&file_colors,&has_palette);
}break;
}
if(has_palette>=0){
/*If we successfully extracted these parameters from the image, override
any declared values.*/
width=file_width;
height=file_height;
depth=file_depth;
colors=file_colors;
}
/*Picture type 1 must be a 32x32 PNG.*/
if(picture_type==1&&(format!=OP_PIC_FORMAT_PNG||width!=32||height!=32)){
return OP_ENOTFORMAT;
}
}
/*Adjust _buf_sz instead of using data_length to capture the terminating NUL
for URLs.*/
_buf_sz-=i;
memmove(_buf,_buf+i,sizeof(*_buf)*_buf_sz);
_buf=(unsigned char *)_ogg_realloc(_buf,_buf_sz);
if(_buf_sz>0&&_buf==NULL)return OP_EFAULT;
_pic->type=picture_type;
_pic->width=width;
_pic->height=height;
_pic->depth=depth;
_pic->colors=colors;
_pic->data_length=data_length;
_pic->data=_buf;
_pic->format=format;
return 0;
}
int opus_picture_tag_parse(OpusPictureTag *_pic,const char *_tag){
OpusPictureTag pic;
unsigned char *buf;
size_t base64_sz;
size_t buf_sz;
size_t tag_length;
int ret;
if(op_strncasecmp(_tag,"METADATA_BLOCK_PICTURE=",23)==0)_tag+=23;
/*Figure out how much BASE64-encoded data we have.*/
tag_length=strlen(_tag);
if(tag_length&3)return OP_ENOTFORMAT;
base64_sz=tag_length>>2;
buf_sz=3*base64_sz;
if(buf_sz<32)return OP_ENOTFORMAT;
if(_tag[tag_length-1]=='=')buf_sz--;
if(_tag[tag_length-2]=='=')buf_sz--;
if(buf_sz<32)return OP_ENOTFORMAT;
/*Allocate an extra byte to allow appending a terminating NUL to URL data.*/
buf=(unsigned char *)_ogg_malloc(sizeof(*buf)*(buf_sz+1));
if(buf==NULL)return OP_EFAULT;
opus_picture_tag_init(&pic);
ret=opus_picture_tag_parse_impl(&pic,_tag,buf,buf_sz,base64_sz);
if(ret<0){
opus_picture_tag_clear(&pic);
_ogg_free(buf);
}
else *_pic=*&pic;
return ret;
}
void opus_picture_tag_init(OpusPictureTag *_pic){
memset(_pic,0,sizeof(*_pic));
}
void opus_picture_tag_clear(OpusPictureTag *_pic){
_ogg_free(_pic->description);
_ogg_free(_pic->mime_type);
_ogg_free(_pic->data);
}