我运行ffmpeg 6.0源代码的avio_read_callback.c示例（ffmpeg-6.0/doc/examples/avio_read_callback.c），输入1080*1920p视频文件时出现错误信息：
./avio_read_callback 1080_1920.mp4
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x1ec23c0] stream 0, offset 0x30: partial file
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x1ec23c0] Could not find codec parameters for stream 0 (Video: h264 (avc1 / 0x31637661), none(tv, bt709), 1920x1080, 2179 kb/s): unspecified pixel format
Consider increasing the value for the 'analyzeduration' (10000000) and 'probesize' (10000000) options
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '1080_1920.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf59.34.102
Duration: 00:01:20.63, start: 0.000000, bitrate: N/A
Stream #0:0[0x1](und): Video: h264 (avc1 / 0x31637661), none(tv, bt709), 1920x1080, 2179 kb/s, SAR 1:1 DAR 16:9, 30 fps, 30 tbr, 15360 tbn (default)
Metadata:
handler_name : VideoHandler
vendor_id : [0][0][0][0]
encoder : Lavc59.37.100 libx264
我尝试使用ffprobe获取视频信息，没问题：
ffprobe -i 1080_1920.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '1080_1920.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf59.34.102
Duration: 00:01:20.63, start: 0.000000, bitrate: 2182 kb/s
Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 2179 kb/s, 30 fps, 30 tbr, 15360 tbn (default)
Metadata:
handler_name : VideoHandler
vendor_id : [0][0][0][0]
encoder : Lavc59.37.100 libx264
然后我尝试使用avformat_open_input(&ctx, file_pash, NULL, NULL)直接打开这个视频文件，然后重新编译，重新运行这个例子，结果显示仍然可以：
./avio_read_callback 1080_1920.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '1080_1920.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf59.34.102
Duration: 00:01:20.63, start: 0.000000, bitrate: 2182 kb/s
Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 2179 kb/s, 30 fps, 30 tbr, 15360 tbn (default)
Metadata:
handler_name : VideoHandler
vendor_id : [0][0][0][0]
encoder : Lavc59.37.100 libx264
我直接更改了打开文件的代码，如下所示：
#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;
}
fmt_ctx->probesize = 100000000;
fmt_ctx->max_analyze_duration = 0;
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, input_filename, 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;
}
不知道为什么自定义会报错？
问题已通过阅读以下内容得到解决： 在此输入链接描述
并发布我的解决方案的内存 IO 查找功能：
struct buffer_data {
uint8_t *ptr;
uint8_t *ori_ptr;
size_t size; ///< size left in the buffer
size_t file_size;
};
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;
}
static int64_t seek(void *opaque, int64_t offset, int whence)
{
struct buffer_data *bd = (struct buffer_data *)opaque;
int64_t ret = -1;
switch (whence) {
case AVSEEK_SIZE:
ret = bd->file_size;
break;
case SEEK_SET:
bd->ptr = bd->ori_ptr + offset;
bd->size = bd->file_size - offset;
ret = offset;
break;
}
return ret;
}
avio_ctx = avio_alloc_context(avio_ctx_buffer, avio_ctx_buffer_size,
0, &bd, &read_packet, NULL, &seek);