错误(活动) E0020 未定义标识符 "AV_NOPTS_VALUE"
时间: 2023-11-04 20:04:46 浏览: 105
这个错误通常是由于编译器无法找到 AV_NOPTS_VALUE 常量定义而产生的。AV_NOPTS_VALUE 是 FFmpeg 中定义的常量,用于表示时间戳无效的情况。您需要包含 FFmpeg 的头文件并链接相应的库才能解决这个问题。具体的方法取决于您使用的编译器和操作系统,您可以查看相关文档或者搜索解决方案。
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 解码器中frame->pkt_dts应该如何计算,基于arm v500
ffmpeg的pkt_dts是根据音视频帧的时间戳(PTS)和码流中每个数据包的时序信息(AVPacket.dts)计算得出的。
在ARMv5平台上,可以使用以下代码来计算pkt_dts:
```
AVFrame *frame;
AVPacket *pkt;
int64_t pts, dts;
// 获取帧的PTS和DTS
pts = frame->pts;
dts = frame->pkt_dts;
// 计算pkt_dts
if (dts != AV_NOPTS_VALUE) {
pkt->dts = av_rescale_q(dts, frame->pkt_timebase, pkt->time_base);
} else {
pkt->dts = AV_NOPTS_VALUE;
}
if (pts != AV_NOPTS_VALUE) {
pkt->pts = av_rescale_q(pts, frame->pkt_timebase, pkt->time_base);
} else {
pkt->pts = pkt->dts;
}
```
其中,av_rescale_q函数用于将时间戳从一个时间基转换为另一个时间基。frame->pkt_timebase表示帧的时间基,pkt->time_base表示数据包的时间基。如果帧的DTS不为AV_NOPTS_VALUE,则使用av_rescale_q函数将其转换为数据包的时间基,得到数据包的DTS;如果帧的PTS不为AV_NOPTS_VALUE,则使用av_rescale_q函数将其转换为数据包的时间基,得到数据包的PTS;否则,使用数据包的DTS作为PTS。
需要注意的是,以上代码仅供参考,实际应用中可能需要根据具体情况进行适当的修改。