* are filled. This situation is handled transparently if you follow the steps
* outlined above.
*
+ * In theory, sending input can result in EAGAIN - this should happen only if
+ * not all output was received. You can use this to structure alternative decode
+ * or encode loops other than the one suggested above. For example, you could
+ * try sending new input on each iteration, and try to receive output if that
+ * returns EAGAIN.
+ *
* End of stream situations. These require "flushing" (aka draining) the codec,
* as the codec might buffer multiple frames or packets internally for
* performance or out of necessity (consider B-frames).
* Unlike with the old video decoding API, multiple frames might result from
* a packet. For audio, splitting the input packet into frames by partially
* decoding packets becomes transparent to the API user. You never need to
- * feed an AVPacket to the API twice.
+ * feed an AVPacket to the API twice (unless it is rejected with EAGAIN - then
+ * no data was read from the packet).
* Additionally, sending a flush/draining packet is required only once.
* - avcodec_encode_video2()/avcodec_encode_audio2():
* Use avcodec_send_frame() to feed input to the encoder, then use
* and will result in undefined behavior.
*
* Some codecs might require using the new API; using the old API will return
- * an error when calling it.
+ * an error when calling it. All codecs support the new API.
+ *
+ * A codec is not allowed to return EAGAIN for both sending and receiving. This
+ * would be an invalid state, which could put the codec user into an endless
+ * loop. The API has no concept of time either: it cannot happen that trying to
+ * do avcodec_send_packet() results in EAGAIN, but a repeated call 1 second
+ * later accepts the packet (with no other receive/flush API calls involved).
+ * The API is a strict state machine, and the passage of time is not supposed
+ * to influence it. Some timing-dependent behavior might still be deemed
+ * acceptable in certain cases. But it must never result in both send/receive
+ * returning EAGAIN at the same time at any point. It must also absolutely be
+ * avoided that the current state is "unstable" and can "flip-flop" between
+ * the send/receive APIs allowing progress. For example, it's not allowed that
+ * the codec randomly decides that it actually wants to consume a packet now
+ * instead of returning a frame, after it just returned EAGAIN on an
+ * avcodec_send_packet() call.
* @}
*/
AV_CODEC_ID_SPEEDHQ,
AV_CODEC_ID_FMVC,
AV_CODEC_ID_SCPR,
+ AV_CODEC_ID_CLEARVIDEO,
+ AV_CODEC_ID_XPM,
/* various PCM "codecs" */
AV_CODEC_ID_FIRST_AUDIO = 0x10000, ///< A dummy id pointing at the start of audio codecs
* 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(EAGAIN): input is not accepted in the current state - user
+ * must read output with avcodec_receive_frame() (once
+ * all output is read, the packet should be resent, and
+ * the call will not fail with EAGAIN).
* 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)
*
* @return
* 0: success, a frame was returned
- * AVERROR(EAGAIN): output is not available right now - user must try
+ * AVERROR(EAGAIN): output is not available in this state - user must try
* to send new input
* AVERROR_EOF: the decoder has been fully flushed, and there will be
* no more output frames
* avctx->frame_size for all frames except the last.
* The final frame may be smaller than avctx->frame_size.
* @return 0 on success, otherwise negative error code:
- * AVERROR(EAGAIN): input is not accepted right now - the frame must be
- * resent after trying to read output packets
+ * AVERROR(EAGAIN): input is not accepted in the current state - user
+ * must read output with avcodec_receive_packet() (once
+ * all output is read, the packet should be resent, and
+ * the call will not fail with EAGAIN).
* AVERROR_EOF: the encoder has been flushed, and no new frames can
* be sent to it
* AVERROR(EINVAL): codec not opened, refcounted_frames not set, it is a
* encoder. Note that the function will always call
* av_frame_unref(frame) before doing anything else.
* @return 0 on success, otherwise negative error code:
- * AVERROR(EAGAIN): output is not available right now - user must try
- * to send input
+ * AVERROR(EAGAIN): output is not available in the current state - user
+ * must try to send input
* AVERROR_EOF: the encoder has been fully flushed, and there will be
* no more output packets
* AVERROR(EINVAL): codec not opened, or it is an encoder
projects / ffmpeg / blobdiff