avio_reading.c

<pre name="code" class="cpp">#include <libavcodec/avcodec.h>#include <libavformat/avformat.h>#include <libavformat/avio.h>#include <libavutil/file.h>struct buffer_data {uint8_t *ptr;size_t size; ///< size left in the buffer};static int read_packet(void *opaque, uint8_t *buf, int buf_size) {struct buffer_data *bd = (struct buffer_data *) opaque;buf_size = FFMIN(buf_size, bd->size);printf("ptr:%p size:%zu\n", bd->ptr, bd->size);/* copy internal buffer data to buf */memcpy(buf, bd->ptr, buf_size);bd->ptr += buf_size;bd->size -= buf_size;return buf_size;}int main(int argc, char *argv[]) {AVFormatContext *fmt_ctx = NULL;                      //Format I/O contextAVIOContext *avio_ctx = NULL;                         //ByteStream I/O contextuint8_t *buffer = NULL, *avio_ctx_buffer = NULL;      //buffer for Inputfile and avio_ctxsize_t buffer_size, avio_ctx_buffer_size = 4096;      //The buffer size is very important for performance. For protocol                                                              //For a typical size is a cache page, 4kb char *input_filename = NULL;                          //The input file name                       int ret = 0;struct buffer_data bd = { 0 };                        //The data struct of buffer.if (argc != 2) {fprintf(stderr, "usage: %s input_file\n""API example program to show how to read from a custom buffer ""accessed through AVIOContext.\n", argv[0]);return 1;}input_filename = argv[1];av_register_all()  //Initialize libavformat and register all muxers,demuxes and protocols /* slurp file content into buffer */ret = av_file_map(input_filename, &buffer, &buffer_size, 0, NULL); if (ret < 0)goto end;/* fill opaque structure used by the AVIOContext read callback */bd.ptr = buffer;bd.size = buffer_size;if (!(fmt_ctx = avformat_alloc_context())) {ret = AVERROR(ENOMEM);goto end;}avio_ctx_buffer = av_malloc(avio_ctx_buffer_size);if (!avio_ctx_buffer) {ret = AVERROR(ENOMEM);goto end;}avio_ctx = avio_alloc_context(avio_ctx_buffer, avio_ctx_buffer_size, 0, &bd,&read_packet, NULL, NULL); //Allocate and initialize an AVIOContext for buffered I/0.if (!avio_ctx) {ret = AVERROR(ENOMEM);goto end;}fmt_ctx->pb = avio_ctx;ret = avformat_open_input(&fmt_ctx, NULL, NULL, NULL);//Open an input stream and read the header.if (ret < 0) {fprintf(stderr, "Could not open input\n");goto end;}ret = avformat_find_stream_info(fmt_ctx, NULL);//Read packets of a media file to get stream information.if (ret < 0) {fprintf(stderr, "Could not find stream information\n");goto end;}av_dump_format(fmt_ctx, 0, input_filename, 0);//Print detailed information about the input or output format.Such as duration,bitrate, streams,container,programs.end: avformat_close_input(&fmt_ctx);/* note: the internal buffer could have changed, and be != avio_ctx_buffer */if (avio_ctx) {av_freep(&avio_ctx->buffer);av_freep(&avio_ctx);}av_file_unmap(buffer, buffer_size);if (ret < 0) {fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));return 1;}return 0;}