FFmpeg 内存输入&输出
[]实例 内存输入/输出
ffmpeg内存编解码
内存输入
关键点就两个:
[*]初始化AVIOContext时, 指定自定义的回调函数指针
//AVIOContext中的缓存
unsigned char* _iobuffer = (unsigned char*)av_malloc(40690);// 注意缓存容器要足够大
AVIOContext* avio = avio_alloc_context(_iobuffer , 40690 , 0 , this, fill_buffer,nullptr,nullptr);
assert( avio != NULL);
pFormatCtx->pb = avio;//给AVFormatContext
if(avformat_open_input(&pFormatCtx,NULL,NULL,NULL)!=0){
printf("Couldn't open inputstream.(无法打开输入流)\n");
return -1;
}
[*]回调函数
///注意缓存 容器 要足够大
int fill_buffer(void * opaque,uint8_t *buf, int bufsize){
SDKSource2Player *instance = static_cast<SDKSource2Player*>( opaque);
callback_data * data =instance->source2->takeDataPacketSync();
memcpy( buf, data->data, data->size);//复制到容器 给 ffmpeg
int size =data->size;
SDKSource2::destoryDataPacket(data);//销毁
return size;
}内存输出
[*]回调函数
//内存输出数据
int fill_buffer_out(void * opaque, uint8_t *buf, int bufsize){
WebSocketPlayer *instance = static_cast<WebSocketPlayer*>( opaque);
instance->onAVPacketOutData(buf,bufsize );
return bufsize;
}
[*]分配
// 内存输出
unsigned char* out_buffer = (unsigned char*)av_malloc(40690);//~40k
AVIOContext* out_avio = avio_alloc_context(out_buffer , 40690 , 1 , this, nullptr,nullptr,nullptr);
assert( out_avio != NULL);
AVOutputFormat *oformat = av_guess_format("mp4", nullptr, nullptr);
ret = avformat_alloc_output_context2(&outAvFormatCtx,oformat,nullptr,nullptr);
outAvFormatCtx->pb = out_avio;
outAvFormatCtx->flags = AVFMT_FLAG_CUSTOM_IO;
[*]踩坑指南
[*]内存输出的时候需要注意 avio_alloc_context 的第三个参数 write_flag=1 表示 可写
[*]输出 AVFormatContext 的flag 需要标记为 AVFMT_FLAG_CUSTOM_IO
...
outAvFormatCtx->pb = out_avio;
outAvFormatCtx->flags = AVFMT_FLAG_CUSTOM_IO;
...
[*]打开输出avio_open的时候, 第二参数不能是 NULL, 即使没有什么意义; ~~貌似自定义输出,不调用也可以 (实测) ~~
avio_open(&outAvFormatCtx->pb, "nothing",AVIO_FLAG_WRITE) ;
if (!outAvFormatCtx->pb ) {
qDebug()<<"错误: format->pd is NULL";
throw ("Error open ouput fail ");
}AVFormatContext 的pd 属性
AVFormatContext 有个 pd 属性指针, 读写数据都是通过它
// ============================
// 自定义 AVIO 输出
// ============================
struct AVIOCtxWrapper {
JNIEnv *env;
jobject wsServer;
jmethodID broadcastFrame;
};
// 将 FFmpeg 封装输出的数据通过 WebSocket 发出
static int write_packet(void *opaque, uint8_t *buf, int buf_size) {
auto *wrapper = (AVIOCtxWrapper *)opaque;
if (!wrapper || !wrapper->env || !wrapper->wsServer) return 0;
jbyteArray arr = wrapper->env->NewByteArray(buf_size);
if (!arr) return 0;
wrapper->env->SetByteArrayRegion(arr, 0, buf_size, reinterpret_cast<const jbyte*>(buf));
wrapper->env->CallVoidMethod(wrapper->wsServer, wrapper->broadcastFrame, arr);
wrapper->env->DeleteLocalRef(arr);
return buf_size;
}
................
// --- 创建输出 fMP4 ---
if (avformat_alloc_output_context2(&out_fmt, nullptr, "mp4", nullptr) < 0) {
LOGE("Failed to alloc output context");
cleanup();
return;
}
out_fmt->flags = AVFMT_FLAG_CUSTOM_IO;
// 注意：write_packet 期望 wrapper 中持有一个有效的 JNIEnv 与 wsServer/global ref
AVIOCtxWrapper wrapper;
wrapper.env = env;
wrapper.wsServer = ctx->wsServer;
wrapper.broadcastFrame = broadcastFrame;
avio = avio_alloc_context(
avioBuffer, 8192, 1, &wrapper,
nullptr,
reinterpret_cast<int (*)(void *, const uint8_t *, int)>(write_packet),
nullptr
);
if (!avio) {
LOGE("avio_alloc_context failed");
cleanup();
return;
}
out_fmt->pb = avio;avio_alloc_context
/**
* I/O context.
*
* - demuxing: either set by the user before avformat_open_input() (then
* the user must close it manually) or set by avformat_open_input().
* - muxing: set by the user before avformat_write_header(). The caller must
* take care of closing / freeing the IO context.
*
* Do NOT set this field if AVFMT_NOFILE flag is set in
* iformat/oformat.flags. In such a case, the (de)muxer will handle
* I/O in some other way and this field will be NULL.
*/
AVIOContext *pb;可参考官方API 关于 avformat_open_input的文档:
If you want to use custom IO, preallocate the format context and set its pb field.
/**
* Allocate and initialize an AVIOContext for buffered I/O. It must be later
* freed with avio_context_free().
*
* @param buffer Memory block for input/output operations via AVIOContext.
* The buffer must be allocated with av_malloc() and friends.
* It may be freed and replaced with a new buffer by libavformat.
* AVIOContext.buffer holds the buffer currently in use,
* which must be later freed with av_free(). (输入输出的'操作容器',必须使用av_malloc()和friends来分配,av_free()释放, AVIOContext.buffer属性保存当前正在使用的)
* @param buffer_size The buffer size is very important for performance.
* For protocols with fixed blocksize it should be set to this blocksize.
* For others a typical size is a cache page, e.g. 4kb.['操作容器' 的大小]
* @param write_flag Set to 1 if the buffer should be writable, 0 otherwise.(如果 '操作容器' 可以写设置为1, 否则设置为0] 简而言之是否可写 /注意是个小坑)
* @param opaque An opaque pointer to user-specific data.[用户数据指针, 回调用]
* @param read_packetA function for refilling the buffer, may be NULL.
* For stream protocols, must never return 0 but rather
* a proper AVERROR code. [读的 回调函数指针]
* @param write_packet A function for writing the buffer contents, may be NULL.
* The function may not change the input buffers content.[写的 回调函数指针]
* @param seek A function for seeking to specified byte position, may be NULL.
*
* @return Allocated AVIOContext or NULL on failure.
*/
AVIOContext *avio_alloc_context(
unsigned char *buffer,
int buffer_size,
int write_flag,
void *opaque,
int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
int64_t (*seek)(void *opaque, int64_t offset, int whence));雷神的博客 - https://blog.csdn.net/leixiaohua1020/article/details/39759163
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