Supose我在内存中有一个完整的视频文件,我想使用libav来解码整个帧。我该怎么办?关键是我可以使用avformat_open_input()函数直接从文件中读取,但我确实需要从存储在内存中的文件中进行读取。
我的AVIOContext实施:
class AVIOMemContext
{
public:
AVIOMemContext(char* videoData, const int videoLen)
{
// Output buffer
bufferSize = 32768;
buffer = static_cast<char*>(av_malloc(bufferSize));
// Internal buffer
pos = 0;
this->videoData = videoData;
this->videoLen = videoLen;
ctx_ = avio_alloc_context((unsigned char*) buffer, bufferSize, AVIO_FLAG_READ, this, &AVIOMemContext::read, &AVIOMemContext::write, &AVIOMemContext::seek);
}
~AVIOMemContext()
{
av_free(videoData);
}
static int read(void *opaque, unsigned char *buf, int buf_size)
{
AVIOMemContext* This = static_cast<AVIOMemContext*>(opaque);
// Read from pos to pos + buf_size
if (This->pos + buf_size > This->videoLen)
{
int len = This->videoLen - This->pos;
memcpy(buf, This->videoData + This->pos, len);
return len;
}
else
{
memcpy(buf, This->videoData + This->pos, buf_size);
return buf_size;
}
}
static int write(void *opaque, unsigned char *buf, int buf_size)
{
/*
AVIOMemContext* This = static_cast<AVIOMemContext*>(opaque);
return fwrite(buf, 1, buf_size, This->f_);
*/
return 0;
}
static int64_t seek(void *opaque, int64_t offset, int whence)
{
AVIOMemContext* This = static_cast<AVIOMemContext*>(opaque);
if (offset + whence > This->videoLen)
{
This->pos = This->videoLen;
return -1;
}
else
{
This->pos = offset + whence;
return 0;
}
}
AVIOContext *get_avio()
{
return ctx_;
}
private:
// Output buffer
int bufferSize;
char* buffer;
// Internal buffer
int pos;
char* videoData;
int videoLen;
AVIOContext* ctx_;
};
我目前的代码:
[...]
av_register_all();
avcodec_register_all();
AVFormatContext* context;
AVCodec* pCodec;
AVPacket packet;
AVCodecContext* pCodecCtx;
int video_stream_index;
int res;
int got_picture;
// Init variables and objects
context = avformat_alloc_context();
AVIOMemContext priv_ctx(videoData, videoLen);
context->pb = priv_ctx.get_avio();
res = avformat_find_stream_info(context, NULL);
if (res < 0)
{
// Error
avformat_free_context(context);
return 0;
}
// Obtain the video stream of the total set of streams
for (unsigned int k = 0; k < context->nb_streams; ++k)
{
if (context->streams[k]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
video_stream_index = k;
context->streams[k]->codec->time_base.den = 90000;
}
pCodecCtx = context->streams[video_stream_index]->codec;
pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
avcodec_open(pCodecCtx, pCodec);
//allocate video frame
AVFrame *pFrame = avcodec_alloc_frame();
unsigned int nFrame = 0;
while (av_read_frame(context, &packet) >= 0)
[...]
提前致谢,
DídacPérez
答案 0 :(得分:3)
您可以创建自己的AVIOContext
。
您必须致电::avio_alloc_context
,然后将其设为AVFormatContext::pb
。
有关详细信息,请参阅我对How can libavformat be used without using other libav libraries?