Windows 10 x64， ffmpeg: 3.1, 预建 dll
这里绝对是新手。
我正在尝试一个非常基本的案例来解码视频文件中的帧，但每次尝试都失败了。最终的代码片段如下所示:
#define __STDC_CONSTANT_MACROS
extern "C" {
#include<libavutil/avutil.h>
#include<libavutil/imgutils.h>
#include <libavformat/avformat.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
}
#include <iostream>
int main(int argc, char **argv) {
AVFormatContext* ctx_format = nullptr;
AVCodecContext* ctx_codec = nullptr;
AVCodec* codec = nullptr;
AVFrame* frame = av_frame_alloc();
int stream_idx;
SwsContext* ctx_sws = nullptr;
const char* fin = argv[1];
AVStream *vid_stream = nullptr;
AVPacket* pkt = av_packet_alloc();
av_register_all();
if (int ret = avformat_open_input(&ctx_format, fin, nullptr, nullptr) != 0) {
std::cout << 1 << std::endl;
return ret;
}
if (avformat_find_stream_info(ctx_format, nullptr) < 0) {
std::cout << 2 << std::endl;
return -1; // Couldn't find stream information
}
av_dump_format(ctx_format, 0, fin, false);
for (int i = 0; i < ctx_format->nb_streams; i++)
if (ctx_format->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
stream_idx = i;
vid_stream = ctx_format->streams[i];
break;
}
if (vid_stream == nullptr) {
std::cout << 4 << std::endl;
return -1;
}
codec = avcodec_find_decoder(vid_stream->codecpar->codec_id);
if (!codec) {
fprintf(stderr, "codec not found\n");
exit(1);
}
ctx_codec = avcodec_alloc_context3(codec);
if(avcodec_parameters_to_context(ctx_codec, vid_stream->codecpar)<0)
std::cout << 512;
if (avcodec_open2(ctx_codec, codec, nullptr)<0) {
std::cout << 5;
return -1;
}
//av_new_packet(pkt, pic_size);
while(av_read_frame(ctx_format, pkt) >= 0){
int ret = avcodec_send_packet(ctx_codec, pkt);
if (ret < 0 || ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
std::cout << "avcodec_send_packet: " << ret << std::endl;
break;
}
if (pkt->stream_index == stream_idx) {
while (ret >= 0) {
ret = avcodec_receive_frame(ctx_codec, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
//std::cout << "avcodec_receive_frame: " << ret << std::endl;
break;
}
std::cout << "frame: " << ctx_codec->frame_number << std::endl;
}
}
av_packet_unref(pkt);
}
avformat_close_input(&ctx_format);
av_packet_unref(pkt);
avcodec_free_context(&ctx_codec);
avformat_free_context(ctx_format);
return 0;
}
它基本上保留所有默认值，并尝试从中读取数据包和解码帧。 avcodec_send_packet 在 while 循环的第一轮或第二轮调用中总是返回负值。
flv 的输出:
> .\streamer_test.exe .\SampleVideo_360x240_5mb.flv
Input #0, flv, from '.\SampleVideo_360x240_5mb.flv':
Metadata:
encoder : Lavf53.24.2
Duration: 00:00:53.32, start: 0.000000, bitrate: 787 kb/s
Stream #0:0: Audio: aac (LC), 48000 Hz, 5.1, fltp, 384 kb/s
Stream #0:1: Video: flv1, yuv420p, 320x240, 500 kb/s, 1k fps, 25 tbr, 1k tbn
frame: 1
[flv @ 000001545edb66c0] Bad picture start code
[flv @ 000001545edb66c0] header damaged
avcodec_send_packet: -1094995529
mp4 输出:
> .\streamer_test.exe .\SampleVideo_360x240_10mb.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '.\SampleVideo_360x240_10mb.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
creation_time : 1970-01-01T00:00:00.000000Z
encoder : Lavf53.24.2
Duration: 00:02:05.95, start: 0.000000, bitrate: 669 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 320x240 [SAR 1:1 DAR 4:3], 282 kb/s, 15 fps, 15 t
br, 15360 tbn, 30 tbc (default)
Metadata:
creation_time : 1970-01-01T00:00:00.000000Z
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, 5.1, fltp, 383 kb/s (default)
Metadata:
creation_time : 1970-01-01T00:00:00.000000Z
handler_name : SoundHandler
[h264 @ 000002e2446a6cc0] Invalid NAL unit size (17191968 > 1007).
[h264 @ 000002e2446a6cc0] Error splitting the input into NAL units.
avcodec_send_packet: -1094995529
mkv 的输出:
> .\streamer_test.exe .\SampleVideo_1280x720_2mb.mkv
Input #0, matroska,webm, from '.\SampleVideo_1280x720_2mb.mkv':
Metadata:
ENCODER : Lavf53.24.2
Duration: 00:00:10.65, bitrate: 1575 kb/s
Stream #0:0: Video: mpeg4 (Simple Profile), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 1k tbn, 25 tbc (de
fault)
Stream #0:1: Audio: aac (LC), 48000 Hz, 5.1, fltp (default)
frame: 1
[mpeg4 @ 000001166798ede0] header damaged
avcodec_send_packet: -1
所以我猜 avcodec_send_packet 调用一定有问题，但无法弄清楚缺少什么。关于原因的任何想法？非常感谢您的帮助!
最佳答案
调用av_read_frame会返回音频/视频流，你需要用不同的AVCodecContext来处理它们。
因为你用avcodec_send_packet发送音频流，但是你的
AVCodecContext 用于视频流，你得到了错误。
看来你只对视频流感兴趣。
更改您的代码
while(av_read_frame(ctx_format, pkt) >= 0){
int ret = avcodec_send_packet(ctx_codec, pkt);
if (ret < 0 || ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
std::cout << "avcodec_send_packet: " << ret << std::endl;
break;
}
if (pkt->stream_index == stream_idx) {
while (ret >= 0) {
ret = avcodec_receive_frame(ctx_codec, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
//std::cout << "avcodec_receive_frame: " << ret << std::endl;
break;
}
std::cout << "frame: " << ctx_codec->frame_number << std::endl;
}
}
av_packet_unref(pkt);
}
以下内容将起作用。
while(av_read_frame(ctx_format, pkt) >= 0){
if (pkt->stream_index == stream_idx) {
int ret = avcodec_send_packet(ctx_codec, pkt);
if (ret < 0 || ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
std::cout << "avcodec_send_packet: " << ret << std::endl;
break;
}
while (ret >= 0) {
ret = avcodec_receive_frame(ctx_codec, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
//std::cout << "avcodec_receive_frame: " << ret << std::endl;
break;
}
std::cout << "frame: " << ctx_codec->frame_number << std::endl;
}
}
av_packet_unref(pkt);
}
使用ffmpeg解码时，记得针对不同的流成对调用avcodec_send_packet/avcodec_receive_frame
关于c++ - ffmpeg 调用 avcodec_send_packet 失败，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44711921/