doc/examples/demuxing_decoding: convert to new decoding API

doc/examples/demuxing_decoding.c

@@ -55,23 +55,8 @@ static AVPacket pkt;
 static int video_frame_count = 0;
 static int audio_frame_count = 0;
 
-static int decode_packet(int *got_frame, int cached)
+static int output_video_frame(AVFrame *frame)
 {
-    int ret = 0;
-    int decoded = pkt.size;
-
-    *got_frame = 0;
-
-    if (pkt.stream_index == video_stream_idx) {
-        /* decode video frame */
-        ret = avcodec_decode_video2(video_dec_ctx, frame, got_frame, &pkt);
-        if (ret < 0) {
-            fprintf(stderr, "Error decoding video frame (%s)\n", av_err2str(ret));
-            return ret;
-        }
-
-        if (*got_frame) {
-
     if (frame->width != width || frame->height != height ||
         frame->format != pix_fmt) {
         /* To handle this change, one could call av_image_alloc again and
@@ -87,8 +72,7 @@ static int decode_packet(int *got_frame, int cached)
         return -1;
     }
 
-            printf("video_frame%s n:%d coded_n:%d\n",
-                   cached ? "(cached)" : "",
+    printf("video_frame n:%d coded_n:%d\n",
            video_frame_count++, frame->coded_picture_number);
 
     /* copy decoded frame to destination buffer:
@@ -99,24 +83,13 @@ static int decode_packet(int *got_frame, int cached)
 
     /* write to rawvideo file */
     fwrite(video_dst_data[0], 1, video_dst_bufsize, video_dst_file);
-        }
-    } else if (pkt.stream_index == audio_stream_idx) {
-        /* decode audio frame */
-        ret = avcodec_decode_audio4(audio_dec_ctx, frame, got_frame, &pkt);
-        if (ret < 0) {
-            fprintf(stderr, "Error decoding audio frame (%s)\n", av_err2str(ret));
-            return ret;
-        }
-        /* Some audio decoders decode only part of the packet, and have to be
-         * called again with the remainder of the packet data.
-         * Sample: fate-suite/lossless-audio/luckynight-partial.shn
-         * Also, some decoders might over-read the packet. */
-        decoded = FFMIN(ret, pkt.size);
+    return 0;
+}
 
-        if (*got_frame) {
+static int output_audio_frame(AVFrame *frame)
+{
     size_t unpadded_linesize = frame->nb_samples * av_get_bytes_per_sample(frame->format);
-            printf("audio_frame%s n:%d nb_samples:%d pts:%s\n",
-                   cached ? "(cached)" : "",
+    printf("audio_frame n:%d nb_samples:%d pts:%s\n",
            audio_frame_count++, frame->nb_samples,
            av_ts2timestr(frame->pts, &audio_dec_ctx->time_base));
 
@@ -129,13 +102,46 @@ static int decode_packet(int *got_frame, int cached)
      * You should use libswresample or libavfilter to convert the frame
      * to packed data. */
     fwrite(frame->extended_data[0], 1, unpadded_linesize, audio_dst_file);
+
+    return 0;
+}
+
+static int decode_packet(AVCodecContext *dec, const AVPacket *pkt)
+{
+    int ret = 0;
+
+    // submit the packet to the decoder
+    ret = avcodec_send_packet(dec, pkt);
+    if (ret < 0) {
+        fprintf(stderr, "Error submitting a packet for decoding (%s)\n", av_err2str(ret));
+        return ret;
     }
+
+    // get all the available frames from the decoder
+    while (ret >= 0) {
+        ret = avcodec_receive_frame(dec, frame);
+        if (ret < 0) {
+            // those two return values are special and mean there is no output
+            // frame available, but there were no errors during decoding
+            if (ret == AVERROR_EOF || ret == AVERROR(EAGAIN))
+                return 0;
+
+            fprintf(stderr, "Error during decoding (%s)\n", av_err2str(ret));
+            return ret;
         }
 
-    if (*got_frame)
+        // write the frame data to output file
+        if (dec->codec->type == AVMEDIA_TYPE_VIDEO)
+            ret = output_video_frame(frame);
+        else
+            ret = output_audio_frame(frame);
+
         av_frame_unref(frame);
+        if (ret < 0)
+            return ret;
+    }
 
-    return decoded;
+    return 0;
 }
 
 static int open_codec_context(int *stream_idx,
@@ -221,7 +227,7 @@ static int get_format_from_sample_fmt(const char **fmt,
 
 int main (int argc, char **argv)
 {
-    int ret = 0, got_frame;
+    int ret = 0;
 
     if (argc != 4) {
         fprintf(stderr, "usage: %s  input_file video_output_file audio_output_file\n"
@@ -309,23 +315,22 @@ int main (int argc, char **argv)
 
     /* read frames from the file */
     while (av_read_frame(fmt_ctx, &pkt) >= 0) {
-        AVPacket orig_pkt = pkt;
-        do {
-            ret = decode_packet(&got_frame, 0);
+        // check if the packet belongs to a stream we are interested in, otherwise
+        // skip it
+        if (pkt.stream_index == video_stream_idx)
+            ret = decode_packet(video_dec_ctx, &pkt);
+        else if (pkt.stream_index == audio_stream_idx)
+            ret = decode_packet(audio_dec_ctx, &pkt);
+        av_packet_unref(&pkt);
         if (ret < 0)
             break;
-            pkt.data += ret;
-            pkt.size -= ret;
-        } while (pkt.size > 0);
-        av_packet_unref(&orig_pkt);
     }
 
-    /* flush cached frames */
-    pkt.data = NULL;
-    pkt.size = 0;
-    do {
-        decode_packet(&got_frame, 1);
-    } while (got_frame);
+    /* flush the decoders */
+    if (video_dec_ctx)
+        decode_packet(video_dec_ctx, NULL);
+    if (audio_dec_ctx)
+        decode_packet(audio_dec_ctx, NULL);
 
     printf("Demuxing succeeded.\n");