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FFTDecoder.m
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//
// FFTDecoder.m
// FFmpegTutorial-macOS
//
// Created by qianlongxu on 2022/7/27.
// Copyright © 2022 Matt Reach's Awesome FFmpeg Tutotial. All rights reserved.
//
// 自定义解码器类
// 通过代理衔接输入输出
#import "FFTDecoder.h"
#import <libavcodec/avcodec.h>
#import <libavformat/avformat.h>
@interface FFTDecoder()
{
//创建一个frame就行了，可以复用
AVFrame *_frame;
}
@property (nonatomic, assign, readwrite) AVStream * stream;
@property (nonatomic, assign) AVCodecContext * avctx;
//for video
@property (nonatomic, assign, readwrite) int format;
@property (nonatomic, assign, readwrite) int picWidth;
@property (nonatomic, assign, readwrite) int picHeight;
@property (nonatomic, assign, readwrite) AVRational frameRate;
//for audio
@property (nonatomic, assign, readwrite) int sampleRate;
@property (nonatomic, assign, readwrite) int channelLayout;
@end
@implementation FFTDecoder
- (void)dealloc
{
//释放解码器上下文
if (_avctx) {
avcodec_free_context(&_avctx);
_avctx = NULL;
}
//释放内存
if (_frame) {
av_frame_free(&_frame);
}
}
- (instancetype)init
{
self = [super init];
if (self) {
_streamIdx = -1;
_frame = av_frame_alloc();
}
return self;
}
- (int)open
{
if (self.ic == NULL) {
return -1;
}
if (self.streamIdx < 0 || self.streamIdx >= self.ic->nb_streams){
return -1;
}
AVStream *stream = self.ic->streams[self.streamIdx];
//创建解码器上下文
AVCodecContext *avctx = avcodec_alloc_context3(NULL);
if (!avctx) {
return AVERROR(ENOMEM);
}
//填充下相关参数
if (avcodec_parameters_to_context(avctx, stream->codecpar)) {
avcodec_free_context(&avctx);
return -1;
}
avctx->pkt_timebase = stream->time_base;
//查找解码器
const AVCodec *codec = avcodec_find_decoder(avctx->codec_id);
if (!codec){
avcodec_free_context(&avctx);
return -1;
}
avctx->codec_id = codec->id;
//打开解码器
if (avcodec_open2(avctx, codec, NULL)) {
avcodec_free_context(&avctx);
return -1;
}
stream->discard = AVDISCARD_DEFAULT;
self.stream = stream;
self.avctx = avctx;
if (avctx->codec_type == AVMEDIA_TYPE_AUDIO) {
self.format = avctx->sample_fmt;
self.sampleRate = avctx->sample_rate;
self.channelLayout = avctx->channel_layout;
} else if (avctx->codec_type == AVMEDIA_TYPE_VIDEO) {
self.format = avctx->pix_fmt;
self.picWidth = avctx->width;
self.picHeight = avctx->height;
self.frameRate = av_guess_frame_rate(self.ic, stream, NULL);
} else {
}
return 0;
}
#pragma mark - 音视频通用解码方法
- (int)decoder_decode_frame:(AVCodecContext *)avctx pkt:(AVPacket *)pkt frame:(AVFrame*)frame
{
int ret = 0;
for (;;) {
do {
//先尝试接收帧
ret = avcodec_receive_frame(avctx, frame);
//成功接收到一个解码帧
if (ret >= 0){
if ([self.delegate respondsToSelector:@selector(decoder:reveivedAFrame:)]) {
[self.delegate decoder:self reveivedAFrame:frame];
}
av_frame_unref(frame);
continue;
}
//结束标志，此次并没有获取到frame！
if (ret == AVERROR_EOF) {
avcodec_flush_buffers(avctx);
if ([self.delegate respondsToSelector:@selector(decoderEof:)]) {
[self.delegate decoderEof:self];
}
goto end;
}
} while (ret != AVERROR(EAGAIN)/*需要更多packet数据*/);
if (pkt) {
//发送给解码器去解码
if (avcodec_send_packet(avctx, pkt) == AVERROR(EAGAIN)) {
av_log(avctx, AV_LOG_ERROR, "Receive_frame and send_packet both returned EAGAIN, which is an API violation.\n");
}
pkt = NULL;
continue;
} else {
break;
}
}
end:
return ret;
}
- (int)sendPacket:(AVPacket *)pkt
{
int r = [self decoder_decode_frame:_avctx pkt:pkt frame:_frame];
return r;
}
@end