[FFmpeg-devel] [PATCH 3/6] avformat/movenc: enable handle_eac3 to handle AC-3 tracks

[Jan Ekström]

From: Jan Ekström <jan.ekstrom at 24i.com>

Add the AC-3 frame type, as well as early exit from additional packet
parsing in case of AC-3, as only a single packet is required to get
the required information.

Additionally, expose ac3_bit_rate_code via the eac3_info struct as
it is required for AC3SpecificBox.

Signed-off-by: Jan Ekström <jan.ekstrom at 24i.com>
---
 libavformat/movenc.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index 63713e5640..2589f2f4bb 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -383,6 +383,7 @@ struct eac3_info {
     /* Layout of the EC3SpecificBox */
     /* maximum bitrate */
     uint16_t data_rate;
+    int8_t   ac3_bit_rate_code;
     /* number of independent substreams */
     uint8_t  num_ind_sub;
     struct {
@@ -413,8 +414,12 @@ static int handle_eac3(MOVMuxContext *mov, AVPacket *pkt, MOVTrack *track)
     struct eac3_info *info;
     int num_blocks, ret;
 
-    if (!track->eac3_priv && !(track->eac3_priv = av_mallocz(sizeof(*info))))
-        return AVERROR(ENOMEM);
+    if (!track->eac3_priv) {
+        if (!(track->eac3_priv = av_mallocz(sizeof(*info))))
+            return AVERROR(ENOMEM);
+
+        ((struct eac3_info *)track->eac3_priv)->ac3_bit_rate_code = -1;
+    }
     info = track->eac3_priv;
 
     if (!info->pkt && !(info->pkt = av_packet_alloc()))
@@ -431,6 +436,8 @@ static int handle_eac3(MOVMuxContext *mov, AVPacket *pkt, MOVTrack *track)
     }
 
     info->data_rate = FFMAX(info->data_rate, hdr->bit_rate / 1000);
+    info->ac3_bit_rate_code = FFMAX(info->ac3_bit_rate_code,
+                                    hdr->ac3_bit_rate_code);
     num_blocks = hdr->num_blocks;
 
     if (!info->ec3_done) {
@@ -442,7 +449,8 @@ static int handle_eac3(MOVMuxContext *mov, AVPacket *pkt, MOVTrack *track)
 
         /* this should always be the case, given that our AC-3 parser
          * concatenates dependent frames to their independent parent */
-        if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) {
+        if (hdr->frame_type == EAC3_FRAME_TYPE_INDEPENDENT ||
+            hdr->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT) {
             /* substream ids must be incremental */
             if (hdr->substreamid > info->num_ind_sub + 1) {
                 ret = AVERROR(EINVAL);
@@ -474,6 +482,14 @@ static int handle_eac3(MOVMuxContext *mov, AVPacket *pkt, MOVTrack *track)
         info->substream[hdr->substreamid].acmod = hdr->channel_mode;
         info->substream[hdr->substreamid].lfeon = hdr->lfe_on;
 
+        if (track->par->codec_id == AV_CODEC_ID_AC3) {
+            // with AC-3 we only require the information of a single packet,
+            // so we can finish as soon as the basic values of the bit stream
+            // have been set to the track's informational structure.
+            info->ec3_done = 1;
+            goto concatenate;
+        }
+
         /* Parse dependent substream(s), if any */
         if (pkt->size != hdr->frame_size) {
             int cumul_size = hdr->frame_size;
-- 
2.36.1