ffmpeg从内存读取数据案例

深碍√TFBOYSˉ_ 2022-10-27 12:24 89阅读 0赞

该案例来自于ffmpeg avio\_reading.c

/* * Copyright (c) 2014 Stefano Sabatini * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */
    
    /** * @file * libavformat AVIOContext API example. * * Make libavformat demuxer access media content through a custom * AVIOContext read callback. * @example avio_reading.c */
    
    #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);
    
        if (!buf_size)
            return AVERROR_EOF;
        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;
        AVIOContext *avio_ctx = NULL;
        uint8_t *buffer = NULL, *avio_ctx_buffer = NULL;
        size_t buffer_size, avio_ctx_buffer_size = 4096;
        char *input_filename = NULL;
        int ret = 0;
        struct buffer_data bd = {  0 };
    
        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];
    
        /* 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);
        if (!avio_ctx) { 
            ret = AVERROR(ENOMEM);
            goto end;
        }
        fmt_ctx->pb = avio_ctx;
    
        ret = avformat_open_input(&fmt_ctx, NULL, NULL, NULL);
        if (ret < 0) { 
            fprintf(stderr, "Could not open input\n");
            goto end;
        }
    
        ret = avformat_find_stream_info(fmt_ctx, NULL);
        if (ret < 0) { 
            fprintf(stderr, "Could not find stream information\n");
            goto end;
        }
    
        av_dump_format(fmt_ctx, 0, input_filename, 0);
    
    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);
        avio_context_free(&avio_ctx);
    
        av_file_unmap(buffer, buffer_size);
    
        if (ret < 0) { 
            fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
            return 1;
        }
    
        return 0;
    }