avformat/rtpdec_ac3: add AC3 RTP depacketization (RFC 4184)

Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Reviewed-by: Thomas Volkert <silvo@gmx.net>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 157 insertions, 0 deletions

diff --git a/libavformat/rtpdec_ac3.c b/libavformat/rtpdec_ac3.c
new file mode 100644
index 0000000000..7454a9af13
--- /dev/null
+++ b/libavformat/rtpdec_ac3.c
@@ -0,0 +1,157 @@
+/*
+ * RTP parser for AC3 payload format (RFC 4184)
+ * Copyright (c) 2015 Gilles Chanteperdrix <gch@xenomai.org>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avformat.h"
+#include "rtpdec_formats.h"
+
+#define RTP_AC3_PAYLOAD_HEADER_SIZE 2
+
+struct PayloadContext {
+    unsigned nr_frames;
+    unsigned last_frame;
+    uint32_t timestamp;
+    AVIOContext *fragment;
+};
+
+static av_cold int ac3_init(AVFormatContext *s, int st_index,
+                        PayloadContext *data)
+{
+    if (st_index < 0)
+        return 0;
+    s->streams[st_index]->need_parsing = AVSTREAM_PARSE_FULL;
+    return 0;
+}
+
+static PayloadContext *ac3_new_context(void)
+{
+    return av_mallocz(sizeof(PayloadContext));
+}
+
+static inline void free_fragment_if_needed(PayloadContext *data)
+{
+    if (data->fragment) {
+        uint8_t *p;
+        avio_close_dyn_buf(data->fragment, &p);
+        av_free(p);
+        data->fragment = NULL;
+    }
+}
+
+static void ac3_free_context(PayloadContext *data)
+{
+    free_fragment_if_needed(data);
+    av_free(data);
+}
+
+static int ac3_handle_packet(AVFormatContext *ctx, PayloadContext *data,
+                              AVStream *st, AVPacket *pkt, uint32_t *timestamp,
+                              const uint8_t *buf, int len, uint16_t seq,
+                              int flags)
+{
+    unsigned frame_type;
+    unsigned nr_frames;
+    int err;
+
+    if (len < RTP_AC3_PAYLOAD_HEADER_SIZE + 1) {
+        av_log(ctx, AV_LOG_ERROR, "Invalid %d bytes packet\n", len);
+        return AVERROR_INVALIDDATA;
+    }
+
+    frame_type = buf[0] & 0x3;
+    nr_frames = buf[1];
+    buf += RTP_AC3_PAYLOAD_HEADER_SIZE;
+    len -= RTP_AC3_PAYLOAD_HEADER_SIZE;
+
+    switch (frame_type) {
+    case 0: /* One or more complete frames */
+        if (!nr_frames) {
+            av_log(ctx, AV_LOG_ERROR, "Invalid AC3 packet data\n");
+            return AVERROR_INVALIDDATA;
+        }
+        if (av_new_packet(pkt, len)) {
+            av_log(ctx, AV_LOG_ERROR, "Out of memory.\n");
+            return AVERROR(ENOMEM);
+        }
+
+        pkt->stream_index = st->index;
+        memcpy(pkt->data, buf, len);
+        return 0;
+
+    case 1:
+    case 2: /* First fragment */
+        free_fragment_if_needed(data);
+
+        data->last_frame = 1;
+        data->nr_frames = nr_frames;
+        err = avio_open_dyn_buf(&data->fragment);
+        if (err < 0)
+            return err;
+
+        avio_write(data->fragment, buf, len);
+        data->timestamp = *timestamp;
+        return AVERROR(EAGAIN);
+
+    case 3: /* Fragment other than first */
+        if (!data->fragment) {
+            av_log(ctx, AV_LOG_WARNING,
+                   "Received packet without a start fragment; dropping.\n");
+            return AVERROR(EAGAIN);
+        }
+        if (nr_frames != data->nr_frames ||
+            data->timestamp != *timestamp) {
+            free_fragment_if_needed(data);
+            av_log(ctx, AV_LOG_ERROR, "Invalid packet received\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        avio_write(data->fragment, buf, len);
+        data->last_frame++;
+    }
+
+    if (!(flags & RTP_FLAG_MARKER))
+        return AVERROR(EAGAIN);
+
+    if (data->last_frame != data->nr_frames) {
+        free_fragment_if_needed(data);
+        av_log(ctx, AV_LOG_ERROR, "Missed %d packets\n",
+               data->nr_frames - data->last_frame);
+        return AVERROR_INVALIDDATA;
+    }
+
+    err = ff_rtp_finalize_packet(pkt, &data->fragment, st->index);
+    if (err < 0) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Error occurred when getting fragment buffer.");
+        return err;
+    }
+
+    return 0;
+}
+
+RTPDynamicProtocolHandler ff_ac3_dynamic_handler = {
+    .enc_name           = "ac3",
+    .codec_type         = AVMEDIA_TYPE_AUDIO,
+    .codec_id           = AV_CODEC_ID_AC3,
+    .init               = ac3_init,
+    .alloc              = ac3_new_context,
+    .free               = ac3_free_context,
+    .parse_packet       = ac3_handle_packet,
+};