ffmpeg3版本的解碼介面做了不少調整，之前的視訊解碼介面avcodec_decode_video2和avcodec_decode_audio4音訊解碼被設定為deprecated，對這兩個介面做了
阿新 • • 發佈：2019-02-18
/**
* Supply raw packet data as input to a decoder.
*
* Internally, this call will copy relevant AVCodecContext fields, which can
* influence decoding per-packet, and apply them when the packet is actually
* decoded. (For example AVCodecContext.skip_frame, which might direct the
* decoder to drop the frame contained by the packet sent with this function.)
*
* @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
* larger than the actual read bytes because some optimized bitstream
* readers read 32 or 64 bits at once and could read over the end.
*
* @warning Do not mix this API with the legacy API (like avcodec_decode_video2())
* on the same AVCodecContext. It will return unexpected results now
* or in future libavcodec versions.
*
* @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
* before packets may be fed to the decoder.
*
* @param avctx codec context
* @param[in] avpkt The input AVPacket. Usually, this will be a single video
* frame, or several complete audio frames.
* Ownership of the packet remains with the caller, and the
* decoder will not write to the packet. The decoder may create
* a reference to the packet data (or copy it if the packet is
* not reference-counted).
* Unlike with older APIs, the packet is always fully consumed,
* and if it contains multiple frames (e.g. some audio codecs),
* will require you to call avcodec_receive_frame() multiple
* times afterwards before you can send a new packet.
* It can be NULL (or an AVPacket with data set to NULL and
* size set to 0); in this case, it is considered a flush
* packet, which signals the end of the stream. Sending the
* first flush packet will return success. Subsequent ones are
* unnecessary and will return AVERROR_EOF. If the decoder
* still has frames buffered, it will return them after sending
* a flush packet.
*
* @return 0 on success, otherwise negative error code:
* AVERROR(EAGAIN): input is not accepted right now - the packet must be
* resent after trying to read output
* AVERROR_EOF: the decoder has been flushed, and no new packets can
* be sent to it (also returned if more than 1 flush
* packet is sent)
* AVERROR(EINVAL): codec not opened, it is an encoder, or requires flush
* AVERROR(ENOMEM): failed to add packet to internal queue, or similar
* other errors: legitimate decoding errors
* Supply raw packet data as input to a decoder.
*
* Internally, this call will copy relevant AVCodecContext fields, which can
* influence decoding per-packet, and apply them when the packet is actually
* decoded. (For example AVCodecContext.skip_frame, which might direct the
* decoder to drop the frame contained by the packet sent with this function.)
*
* @warning The input buffer, avpkt->data must be AV_INPUT_BUFFER_PADDING_SIZE
* larger than the actual read bytes because some optimized bitstream
* readers read 32 or 64 bits at once and could read over the end.
*
* @warning Do not mix this API with the legacy API (like avcodec_decode_video2())
* on the same AVCodecContext. It will return unexpected results now
* or in future libavcodec versions.
*
* @note The AVCodecContext MUST have been opened with @ref avcodec_open2()
* before packets may be fed to the decoder.
*
* @param avctx codec context
* @param[in] avpkt The input AVPacket. Usually, this will be a single video
* frame, or several complete audio frames.
* Ownership of the packet remains with the caller, and the
* decoder will not write to the packet. The decoder may create
* a reference to the packet data (or copy it if the packet is
* not reference-counted).
* Unlike with older APIs, the packet is always fully consumed,
* and if it contains multiple frames (e.g. some audio codecs),
* will require you to call avcodec_receive_frame() multiple
* times afterwards before you can send a new packet.
* It can be NULL (or an AVPacket with data set to NULL and
* size set to 0); in this case, it is considered a flush
* packet, which signals the end of the stream. Sending the
* first flush packet will return success. Subsequent ones are
* unnecessary and will return AVERROR_EOF. If the decoder
* still has frames buffered, it will return them after sending
* a flush packet.
*
* @return 0 on success, otherwise negative error code:
* AVERROR(EAGAIN): input is not accepted right now - the packet must be
* resent after trying to read output
* AVERROR_EOF: the decoder has been flushed, and no new packets can
* be sent to it (also returned if more than 1 flush
* packet is sent)
* AVERROR(EINVAL): codec not opened, it is an encoder, or requires flush
* AVERROR(ENOMEM): failed to add packet to internal queue, or similar
* other errors: legitimate decoding errors