我将尝试将多个ogg vorbis文件合并为一个。
理论上,只需要执行以下操作即可:
cat 1.ogg 2.ogg > combined.ogg
但这样做也有不足之处:
- 不是所有的播放器都支持像这样创建的文件(如gstreamer)
- 那些支持的播放器也不能平滑地连接它们,而是会产生难看的瞬间暂停
- 似乎无法进行跳转
我不想失去音质,所以我可以将它们重新编码为类似flac这样的无损格式,但这会让文件大小急剧增加。
目前似乎没有这样的工具。例如,oggCat会重新编码音频,从而导致轻微的质量损失,而ffmpeg的concat demuxer并不适用于所有输入文件。我在这个超级用户问题中寻找了一个工具,但当我发现没有时,就自己写了一个。
因此,我尝试使用libogg和libvorbis手动将输入文件中的ogg数据包连接到输出文件的ogg页面中。假设所有的ogg输入文件都是使用完全相同的参数进行编码的。
以下是我的代码:
#include <ogg/ogg.h>
#include <vorbis/codec.h>
#include <stdio.h>
#include <unistd.h>
#include <stdbool.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <time.h>
int read_page(int fd, ogg_sync_state *state, ogg_page *page)
{
int ret;
ssize_t bytes;
while(ogg_sync_pageout(state, page) != 1) {
char *buffer = ogg_sync_buffer(state, 4096);
if (buffer == NULL) {
fprintf(stderr, "ogg_sync_buffer failed\n");
return -1;
}
bytes = read(fd, buffer, 4096);
if (bytes == 0) {
return -1;
}
ret = ogg_sync_wrote(state, bytes);
if (ret != 0) {
fprintf(stderr, "ogg_sync_wrote failed\n");
return -1;
}
}
return 0;
}
int main(int argc, char *argv[])
{
int ret;
ogg_sync_state state;
ogg_page page;
int serial;
ogg_stream_state sstate;
bool found_bos;
ogg_packet packet;
int fd;
int i;
vorbis_info info;
vorbis_comment comment;
int vorbis_header_read;
ssize_t bytes;
ogg_stream_state out_stream;
ogg_page out_page;
if (argc < 2) {
fprintf(stderr, "usage: %s file.ogg\n", argv[0]);
return 1;
}
srand(time(NULL));
ogg_stream_init(&out_stream, rand());
// go through all input files
for (i = 1; i < argc; i++) {
vorbis_header_read = 0;
found_bos = false;
fd = open(argv[i], O_RDONLY);
if (fd < 0) {
fprintf(stderr, "cannot open %s\n", argv[1]);
return 1;
}
ret = ogg_sync_init(&state);
if (ret != 0) {
fprintf(stderr, "ogg_sync_init failed\n");
return 1;
}
vorbis_info_init(&info);
vorbis_comment_init(&comment);
// go through all ogg pages
while (read_page(fd, &state, &page) == 0) {
serial = ogg_page_serialno(&page);
if (ogg_page_bos(&page)) {
if (found_bos) {
fprintf(stderr, "cannot handle more than one stream\n");
return 1;
}
ret = ogg_stream_init(&sstate, serial);
if (ret != 0) {
fprintf(stderr, "ogg_stream_init failed\n");
return 1;
}
found_bos = true;
}
if (!found_bos) {
fprintf(stderr, "cannot continue without bos\n");
return 1;
}
ret = ogg_stream_pagein(&sstate, &page);
if (ret != 0) {
fprintf(stderr, "ogg_stream_pagein failed\n");
return 1;
}
// if this is the last page, then only write it if we are in the
// last file
if (ogg_page_eos(&page) && i != argc - 1) {
continue;
}
// go through all (hopefully vorbis) packets
while((ret = ogg_stream_packetout(&sstate, &packet)) != 0) {
if (ret != 1) {
fprintf(stderr, "ogg_stream_packetout failed\n");
return 1;
}
// test if this stream is vorbis
if (vorbis_header_read == 0) {
ret = vorbis_synthesis_idheader(&packet);
if (ret == 0) {
fprintf(stderr, "stream is not vorbis\n");
return 1;
}
}
// read exactly three vorbis headers
if (vorbis_header_read < 3) {
ret = vorbis_synthesis_headerin(&info, &comment, &packet);
if (ret != 0) {
fprintf(stderr, "vorbis_synthesis_headerin failed\n");
return 1;
}
// if this is the first file, copy the header packet to the
// output
if (i == 1) {
ret = ogg_stream_packetin(&out_stream, &packet);
if (ret != 0) {
fprintf(stderr, "ogg_stream_packetin failed\n");
return 1;
}
}
vorbis_header_read++;
continue;
}
// if this is the first file, write a page to the output
if (vorbis_header_read == 3 && i == 1) {
while ((ret = ogg_stream_flush(&out_stream, &out_page)) != 0) {
bytes = write(STDOUT_FILENO, out_page.header, out_page.header_len);
if (bytes != out_page.header_len) {
fprintf(stderr, "write failed\n");
return 1;
}
bytes = write(STDOUT_FILENO, out_page.body, out_page.body_len);
if (bytes != out_page.body_len) {
fprintf(stderr, "write failed\n");
return 1;
}
}
vorbis_header_read++;
}
ogg_stream_packetin(&out_stream, &packet);
do {
ret = ogg_stream_pageout(&out_stream, &out_page);
if (ret == 0) break;
bytes = write(STDOUT_FILENO, out_page.header, out_page.header_len);
if (bytes != out_page.header_len) {
fprintf(stderr, "write failed\n");
return 1;
}
bytes = write(STDOUT_FILENO, out_page.body, out_page.body_len);
if (bytes != out_page.body_len) {
fprintf(stderr, "write failed\n");
return 1;
}
} while (!ogg_page_eos(&out_page));
}
}
vorbis_info_clear(&info);
vorbis_comment_clear(&comment);
ret = ogg_sync_clear(&state);
if (ret != 0) {
fprintf(stderr, "ogg_sync_clear failed\n");
return 1;
}
ret = ogg_stream_clear(&sstate);
if (ret != 0) {
fprintf(stderr, "ogg_stream_clear failed\n");
return 1;
}
close(fd);
}
ogg_stream_clear(&out_stream);
return 0;
}
这个方案基本可行,但是在连接vorbis流的地方会插入几乎听不见的点击声。
如何正确地实现?
这是否有可能实现?