Audio 如何在ogg vorbis文件中查找而不将所有文件加载到内存中？
我试图找到一种方法，在不将所有文件加载到内存的情况下，移动到曲目中所需的位置。而不使用Audio 如何在ogg vorbis文件中查找而不将所有文件加载到内存中？,audio,codec,ogg,seek,vorbis,Audio,Codec,Ogg,Seek,Vorbis,我试图找到一种方法，在不将所有文件加载到内存的情况下，移动到曲目中所需的位置。而不使用vorbisfile，因为该文件存储在远程服务器中。我阅读了文档中关于查找的段落，但无法理解。如果远程服务器允许您使用带有范围头的HTTP GET，您可以通过发送一系列不同部分的请求来“伪造”文件访问，就像您对本地文件一样 假设：文件是Ogg封装的，其中只有Vorbis流 执行HTTP HEAD请求以获取文件的总长度 获取文件的前4KB并“同步”Vorbis头。您可能需要获取更多数据才能完成此操作 获取文件的最
vorbisfile请记住，颗粒位置是页面末尾的样本计数，因此当您找到正确的页面时，其颗粒位置将略大于您的目标位置。如果远程服务器允许您将HTTP GET与范围标头一起使用，您可以“伪造”通过发送对不同部分的一系列请求来访问文件，就像对本地文件一样 假设：文件是Ogg封装的，其中只有Vorbis流
请记住，颗粒位置是页面末尾的样本数，因此当您找到正确的页面时，其颗粒位置将略大于您的目标位置。查找ogg文件很困难 要理解的事情清单
int buffer_data(){
//oy is an ogg_sync_state https://xiph.org/ogg/doc/libogg/ogg_sync_state.html
//in is just a file
char *buffer=ogg_sync_buffer(&oy,4096);
int bytes=fread(buffer,1,4096,&in);
ogg_sync_wrote(&oy,bytes);
return(bytes);
}
#include <unordered_map>
struct _page_info {
size_t block_number;
double_t time;
ogg_int64_t granulepos;
};
struct _page_info left_page = { .time = 0, .block_number = 0, .granulepos = 0 };
struct _page_info mid_page = { .time = 0, .block_number = 0, .granulepos = 0 };
struct _page_info right_page = { .time = DBL_MAX, .block_number = 0x7FFFFFFFFFFFFFFF, .granulepos = 0x7FFFFFFFFFFFFFFF };
unordered_map<int, double> block_time;
unordered_map<ogg_int64_t, _page_info> page_info_table;
ogg_page og;
while (left <= right) {
//Seek to block
size_t mid_block = left + (right - left) / 2;
int block = mid_block;
if (block_time.has(block)) {
//Check whether this block has been visited
break;
}
//clear the sync state
ogg_sync_reset(&oy);
file.seek(block * buffer_size);
buffer_data();
bool next_midpoint = true;
while (true) {
//keep syncing until a page is found. Buffer is only 4k while ogg pages can be up to 65k in size
int ogg_page_sync_state = ogg_sync_pageout(&oy, &og);
if (ogg_page_sync_state == -1) {
//Give up when the file advances past the right boundary
if (buffer_data() == 0) {
right = mid_block;
break;
} else {
//increment block size we buffered the next block
block++;
}
} else {
if (ogg_page_sync_state == 0) {
//Check if I reached the end of the file
if (buffer_data() == 0) {
right = mid_block;
break;
} else {
block++;
}
} else {
//Only pages with a end packet have granulepos. Check the stream
if (ogg_page_packets(&og) > 0 && ogg_page_serialno(&og) == vo.serialno) {
next_midpoint = false;
break;
}
}
}
}
if (next_midpoint)
continue;
ogg_int64_t granulepos = ogg_page_granulepos(&og);
ogg_int64_t page_number = ogg_page_pageno(&og);
struct _page_info pg_info = { .time = vorbis_granule_time(vd, granulepos), .block_number = mid_block, .granulepos = granulepos };
page_info_table[page_number] = pg_info;
block_time[mid_block] = pg_info.time;
mid_page = pg_info;
//I can finally implement the binary search comparisons
if (abs(p_time - pg_info.time) < .001) {
//The video managed to be equal
right_page = pg_info;
break;
}
if (pg_info.time > p_time) {
if (pg_info.granulepos < right_page.granulepos)
right_page = pg_info;
right = mid_block;
} else {
if (pg_info.granulepos > left_page.granulepos)
left_page = pg_info;
left = mid_block;
}
}
查找ogg文件很难 要理解的事情清单
int buffer_data(){
//oy is an ogg_sync_state https://xiph.org/ogg/doc/libogg/ogg_sync_state.html
//in is just a file
char *buffer=ogg_sync_buffer(&oy,4096);
int bytes=fread(buffer,1,4096,&in);
ogg_sync_wrote(&oy,bytes);
return(bytes);
}