Question

我使用avformat_alloc_context和avio_alloc_context实现自定义io，以便能够实时读取另一个函数的输出。此函数在boost asio线程中填充缓冲区，而ffmpeg正在从另一个线程读取此缓冲区。

我初始化此函数写入的io缓冲区，以及ffmpeg读取的内容：

BufferData input_buffer = {0};
input_buffer.size = 65536;
input_buffer.ptr = (uint8_t *) av_malloc(buf_size);
memset(input_buffer.ptr,'0',100); 

fprintf(stdout, "initialisation: buffer pointer %p buffer data pointer: %p\n", &input_buffer, input_buffer.ptr);

为什么我要做memset is explained here。然后测试我做的指针地址：

BufferData * decode_buffer;
decode_buffer->size = 65536;
decode_buffer->ptr = (uint8_t *) av_malloc(decode_buffer->size);

AVIOContext * av_io_ctx = avio_alloc_context(decode_buffer->ptr, decode_buffer->size, 0, &input_buffer, &read_function, NULL, NULL);

AVFormatContext *av_fmt_ctx = avformat_alloc_context();
av_fmt_ctx->pb = av_io_ctx;


BufferData * tmpPtr = (BufferData * ) video_input_file->av_io_ctx->opaque;

fprintf(stdout, "video decoder before: buffer pointer %p, buffer data pointer: %p\n", tmpPtr, tmpPtr->ptr);

open_res = avformat_open_input(&av_fmt_ctx, "anyname", in_fmt, options ? &options : NULL);

fprintf(stdout, "video decoder after: buffer pointer %p, buffer data pointer: %p\n", tmpPtr, tmpPtr->ptr);

供参考

typedef struct {
    uint8_t *ptr;
    size_t size;
} BufferData;

读取功能

static int read_function(void* opaque, uint8_t* buf, int buf_size) {
    BufferData *bd = (BufferData *) opaque;
    buf_size = FFMIN(buf_size, bd->size);
    memcpy(buf, bd->ptr, buf_size);
    bd->ptr  += buf_size; //This seemed to cause the problem
    bd->size -= buf_size;
    return buf_size;
}

结果将是：

initialisation: buffer pointer 0x7f2c4a613620, buffer data pointer: 0x7f2c48c56040

video decoder before: buffer pointer 0x7f2c4a613620, buffer data pointer: 0x7f2c48c56040

video decoder after: buffer pointer 0x7f2c4a613620, buffer data pointer: 0x7f2c49e24b50

通过avformat_open_input更改缓冲区数据ptr是否正常？因为我想保留初始指针地址，因为我在另一个函数中使用它，并且已经将它所需的内存磁盘化了。

Answer 1

这与我的阅读功能有关，与avformat_open_input无关。我把指针写成per described here（参见read_packet函数）。在考虑之后更多是的，这是有意义的，因为read函数应该将指针递增到下一帧的开头。

C

1 个答案: