pkt0['frame'].number怎么写代码
时间: 2023-10-15 20:06:03 浏览: 16
可以通过以下方式访问pkt0字典中'frame'键的值并获取它的number属性:
```python
pkt0['frame'].number
```
请注意,该代码假定已经定义了一个名为pkt0的字典,其中包含一个名为'frame'的键,其值是一个对象或字典,该对象或字典具有一个名为'number'的属性或键。
相关问题
ffmpeg音频解码av_frame_alloc
av_frame_alloc函数用于为AVFrame结构体分配内存空间,AVFrame结构体用于存储解码后的音视频数据。在音频解码中,可以通过调用该函数为AVFrame结构体分配内存空间,然后将解码后的音频数据存储到该结构体中,最后再进行后续的处理操作。
具体使用方法如下:
```c
AVFrame *frame = av_frame_alloc();
if (!frame) {
// 内存分配失败处理
}
```
其中,AVFrame结构体的定义如下:
```c
typedef struct AVFrame {
/**
* pointers to the data planes/channels.
* This might be different from the first allocated byte
*/
uint8_t *data[AV_NUM_DATA_POINTERS];
/**
* For video, size in bytes of each picture line.
* For audio, size in bytes of each plane.
*/
int linesize[AV_NUM_DATA_POINTERS];
/**
* pointers to the start of each picture line.
* This is used for both video and audio.
*/
uint8_t **extended_data;
/**
* width and height of the video frame
*/
int width, height;
/**
* number of audio samples (per channel) described by this frame
*/
int nb_samples;
/**
* format of the frame, -1 if unknown or unset
* Values correspond to enum AVPixelFormat for video frames,
* enum AVSampleFormat for audio)
*/
int format;
/**
* 1 -> keyframe, 0-> not
*/
int key_frame;
/**
* Picture type of the frame.
*/
enum AVPictureType pict_type;
/**
* Quality (between 1 (good) and FF_LAMBDA_MAX (bad)).
*/
int quality;
/**
* for AV_PIX_FMT_*_BE formats, linesize alignment
*/
int64_t best_effort_timestamp;
/**
* PTS copied from the AVPacket that was decoded to produce this frame.
*/
int64_t pkt_pts;
/**
* DTS copied from the AVPacket that triggered returning this frame.
*/
int64_t pkt_dts;
/**
* duration of the corresponding packet, expressed in
* AVStream->time_base units, 0 if unknown.
*/
int64_t pkt_duration;
uint64_t metadata;
int decode_error_flags;
/**
* number of audio channels
*/
int channels;
/**
* size of the corresponding packet containing the compressed
* frame. It is set to a negative value if unknown.
*/
int pkt_size;
/**
* data type
*/
enum AVSampleFormat sample_fmt;
/**
* presentation timestamp in timebase units
* (time when frame should be shown to user)
* If AV_NOPTS_VALUE then frame_rate = 1/time_base will be assumed.
*/
int64_t pts;
/**
* reordered PTS from the last AVPacket that has been input into the decoder
*/
int64_t best_effort_timestamp;
/**
* sample aspect ratio (0 if unknown)
* - encoding: Set by user.
* - decoding: Set by libavcodec.
*/
AVRational sample_aspect_ratio;
/**
* motion vector table, used for MPEG1/2/4 and H.263 decoding
*/
struct AVPanScan *pan_scan;
/**
* macroblock decision mode
*/
int coded_picture_number;
int display_picture_number;
/**
* quality (between 1 (good) and FF_LAMBDA_MAX (bad))
*/
int quality;
/**
* buffer age (1->was last buffer and dint change, 2->..., ...)
*/
int age;
/**
* is this picture used as reference
*/
int reference;
/**
* QP table
*/
int8_t *qp_table_buf;
/**
* QP store stride
*/
int qp_table_linesize;
/**
* QP values for each macroblock
*/
int8_t *qp_table;
/**
* For hwaccel-format frames, this should be a reference to the
* AVHWFramesContext describing the frame.
* For normal-format frames, this should be NULL.
*/
AVBufferRef *hw_frames_ctx;
} AVFrame;
```
需要注意的是,AVFrame结构体中的成员变量很多,具体使用哪些成员变量取决于具体的应用场景和需求。
ffmpeg音频解码成wav格式实现代码
以下是使用FFmpeg将音频解码为WAV格式的示例代码:
```
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <inttypes.h>
#include <math.h>
#include <libavutil/channel_layout.h>
#include <libavutil/common.h>
#include <libavutil/frame.h>
#include <libavutil/opt.h>
#include <libavutil/samplefmt.h>
#include <libavutil/timestamp.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswresample/swresample.h>
#define AUDIO_INBUF_SIZE 20480
#define AUDIO_REFILL_THRESH 4096
static void decode(AVCodecContext *dec_ctx, AVPacket *pkt, AVFrame *frame,
FILE *outfile)
{
int i, ch;
int ret, data_size;
/* send the packet with the compressed data to the decoder */
ret = avcodec_send_packet(dec_ctx, pkt);
if (ret < 0) {
fprintf(stderr, "Error submitting the packet to the decoder\n");
exit(1);
}
/* read all the output frames (in general there may be any number of them) */
while (ret >= 0) {
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
return;
else if (ret < 0) {
fprintf(stderr, "Error during decoding\n");
exit(1);
}
data_size = av_get_bytes_per_sample(dec_ctx->sample_fmt);
if (data_size < 0) {
/* This should not occur, checking just for paranoia */
fprintf(stderr, "Failed to calculate data size\n");
exit(1);
}
for (i = 0; i < frame->nb_samples; i++)
for (ch = 0; ch < dec_ctx->channels; ch++)
fwrite(frame->data[ch] + data_size*i, 1, data_size, outfile);
}
}
int main(int argc, char **argv)
{
AVCodec *codec;
AVCodecContext *codec_ctx = NULL;
AVCodecParserContext *parser = NULL;
AVFormatContext *fmt_ctx = NULL;
AVPacket *pkt = NULL;
AVFrame *frame = NULL;
uint8_t inbuf[AUDIO_INBUF_SIZE + AV_INPUT_BUFFER_PADDING_SIZE];
int inbuf_size;
int64_t pts;
int ret;
int i;
if (argc <= 1) {
fprintf(stderr, "Usage: %s <input file>\n", argv[0]);
exit(0);
}
/* register all the codecs */
av_register_all();
/* allocate the input buffer */
pkt = av_packet_alloc();
if (!pkt) {
fprintf(stderr, "Failed to allocate packet\n");
exit(1);
}
/* open the input file */
ret = avformat_open_input(&fmt_ctx, argv[1], NULL, NULL);
if (ret < 0) {
fprintf(stderr, "Cannot open input file '%s'\n", argv[1]);
exit(1);
}
/* retrieve stream information */
ret = avformat_find_stream_info(fmt_ctx, NULL);
if (ret < 0) {
fprintf(stderr, "Cannot find stream information\n");
exit(1);
}
/* select the audio stream */
ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &codec, 0);
if (ret < 0) {
fprintf(stderr, "Cannot find an audio stream in the input file\n");
exit(1);
}
int audio_stream_idx = ret;
/* allocate the codec context */
codec_ctx = avcodec_alloc_context3(codec);
if (!codec_ctx) {
fprintf(stderr, "Failed to allocate codec context\n");
exit(1);
}
/* fill the codec context based on the stream information */
ret = avcodec_parameters_to_context(codec_ctx, fmt_ctx->streams[audio_stream_idx]->codecpar);
if (ret < 0) {
fprintf(stderr, "Failed to copy codec parameters to codec context\n");
exit(1);
}
/* init the codec context */
ret = avcodec_open2(codec_ctx, codec, NULL);
if (ret < 0) {
fprintf(stderr, "Failed to open codec\n");
exit(1);
}
/* allocate the frame */
frame = av_frame_alloc();
if (!frame) {
fprintf(stderr, "Failed to allocate frame\n");
exit(1);
}
/* init the packet parser */
parser = av_parser_init(codec_ctx->codec_id);
if (!parser) {
fprintf(stderr, "Failed to init packet parser\n");
exit(1);
}
/* open the output file */
FILE *outfile = fopen("output.wav", "wb");
if (!outfile) {
fprintf(stderr, "Failed to open output file\n");
exit(1);
}
/* read packets from the input file */
while (1) {
/* get more data from the input file */
ret = av_read_frame(fmt_ctx, pkt);
if (ret < 0)
break;
/* if this is not the audio stream, ignore it */
if (pkt->stream_index != audio_stream_idx) {
av_packet_unref(pkt);
continue;
}
/* send the packet to the parser */
inbuf_size = pkt->size;
memcpy(inbuf, pkt->data, inbuf_size);
while (inbuf_size > 0) {
ret = av_parser_parse2(parser, codec_ctx, &pkt->data, &pkt->size,
inbuf, inbuf_size, AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0);
if (ret < 0) {
fprintf(stderr, "Error while parsing\n");
exit(1);
}
inbuf += ret;
inbuf_size -= ret;
/* if we have a complete frame, decode it */
if (pkt->size > 0) {
decode(codec_ctx, pkt, frame, outfile);
}
}
av_packet_unref(pkt);
}
/* flush the decoder */
decode(codec_ctx, NULL, frame, outfile);
/* close the output file */
fclose(outfile);
/* free the resources */
av_parser_close(parser);
avcodec_free_context(&codec_ctx);
av_frame_free(&frame);
av_packet_free(&pkt);
avformat_close_input(&fmt_ctx);
return 0;
}
```
这个程序使用FFmpeg库将音频文件解码为WAV格式,并将解码后的数据写入到一个输出文件中。你可以将输入文件的路径作为程序的参数来运行它。