[FFmpeg-devel] [PATCH v2 4/6] avformat/mux: add proper support for full N:M bitstream filtering

[Marton Balint]

Previously only 1:1 bitstream filters were supported, the end of the stream was
not signalled to the bitstream filters and time base changes were ignored.

Signed-off-by: Marton Balint <cus at passwd.hu>
---
 libavformat/mux.c | 91 ++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 57 insertions(+), 34 deletions(-)

diff --git a/libavformat/mux.c b/libavformat/mux.c
index 4118d221e0..c2b6d4461e 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -822,14 +822,13 @@ static int prepare_input_packet(AVFormatContext *s, AVPacket *pkt)
     return 0;
 }
 
-static int do_packet_auto_bsf(AVFormatContext *s, AVPacket *pkt) {
-    AVStream *st = s->streams[pkt->stream_index];
+static int need_auto_bsf(AVFormatContext *s, AVStream *st, AVPacket *pkt) {
     int ret;
 
     if (!(s->flags & AVFMT_FLAG_AUTO_BSF))
-        return 1;
+        return 0;
 
-    if (s->oformat->check_bitstream) {
+    if (pkt && s->oformat->check_bitstream) {
         if (!st->internal->bitstream_checked) {
             if ((ret = s->oformat->check_bitstream(s, pkt)) < 0)
                 return ret;
@@ -838,31 +837,7 @@ static int do_packet_auto_bsf(AVFormatContext *s, AVPacket *pkt) {
         }
     }
 
-    if (st->internal->bsfc) {
-        AVBSFContext *ctx = st->internal->bsfc;
-        // TODO: when any bitstream filter requires flushing at EOF, we'll need to
-        // flush each stream's BSF chain on write_trailer.
-        if ((ret = av_bsf_send_packet(ctx, pkt)) < 0) {
-            av_log(ctx, AV_LOG_ERROR,
-                    "Failed to send packet to filter %s for stream %d\n",
-                    ctx->filter->name, pkt->stream_index);
-            return ret;
-        }
-        // TODO: when any automatically-added bitstream filter is generating multiple
-        // output packets for a single input one, we'll need to call this in a loop
-        // and write each output packet.
-        if ((ret = av_bsf_receive_packet(ctx, pkt)) < 0) {
-            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
-                return 0;
-            av_log(ctx, AV_LOG_ERROR,
-                    "Failed to receive packet from filter %s for stream %d\n",
-                    ctx->filter->name, pkt->stream_index);
-            if (s->error_recognition & AV_EF_EXPLODE)
-                return ret;
-            return 0;
-        }
-    }
-    return 1;
+    return !!st->internal->bsfc;
 }
 
 static int interleaved_write_packet(AVFormatContext *s, AVPacket *pkt, int flush);
@@ -889,17 +864,56 @@ static int write_packet_common(AVFormatContext *s, AVStream *st, AVPacket *pkt,
     }
 }
 
+static int write_packets_from_bsfs(AVFormatContext *s, AVStream *st, AVPacket *pkt, int interleaved)
+{
+    AVBSFContext *bsfc = st->internal->bsfc;
+    AVPacket opkt = {0};
+    int ret;
+
+    if ((ret = av_bsf_send_packet(bsfc, pkt)) < 0) {
+        av_log(s, AV_LOG_ERROR,
+                "Failed to send packet to filter %s for stream %d\n",
+                bsfc->filter->name, st->index);
+        return ret;
+    }
+
+    do {
+        ret = av_bsf_receive_packet(bsfc, &opkt);
+        if (ret < 0) {
+            if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
+                ret = 0;
+            if (ret < 0) {
+                av_log(s, AV_LOG_ERROR, "Error applying bitstream filters to an output "
+                       "packet for stream #%d: %s\n", st->index, av_err2str(ret));
+                if (!(s->error_recognition & AV_EF_EXPLODE) && ret != AVERROR(ENOMEM))
+                    continue;
+            }
+            return ret;
+        }
+        av_packet_rescale_ts(&opkt, bsfc->time_base_out, st->time_base);
+        ret = write_packet_common(s, st, &opkt, interleaved);
+        if (!interleaved) // write_packet_common already unrefed opkt for interleaved
+            av_packet_unref(&opkt);
+    } while (ret >= 0);
+
+    return ret;
+}
+
 static int write_packets_common(AVFormatContext *s, AVStream *st, AVPacket *pkt, int interleaved)
 {
     int ret = prepare_input_packet(s, pkt);
     if (ret < 0)
         return ret;
 
-    ret = do_packet_auto_bsf(s, pkt);
-    if (ret <= 0)
+    ret = need_auto_bsf(s, st, pkt);
+    if (ret < 0)
         return ret;
 
-    return write_packet_common(s, st, pkt, interleaved);
+    if (ret) {
+        return write_packets_from_bsfs(s, st, pkt, interleaved);
+    } else {
+        return write_packet_common(s, st, pkt, interleaved);
+    }
 }
 
 int av_write_frame(AVFormatContext *s, AVPacket *in)
@@ -1254,9 +1268,18 @@ int av_interleaved_write_frame(AVFormatContext *s, AVPacket *pkt)
 
 int av_write_trailer(AVFormatContext *s)
 {
-    int ret, i;
+    int i, ret1, ret = 0;
 
-    ret = interleaved_write_packet(s, NULL, 1);
+    for (i = 0; i < s->nb_streams; i++) {
+        if (need_auto_bsf(s, s->streams[i], NULL)) {
+            ret1 = write_packets_from_bsfs(s, s->streams[i], NULL, 1/*interleaved*/);
+            if (ret >= 0)
+                ret = ret1;
+        }
+    }
+    ret1 = interleaved_write_packet(s, NULL, 1);
+    if (ret >= 0)
+        ret = ret1;
 
     if (s->oformat->write_trailer) {
         if (!(s->oformat->flags & AVFMT_NOFILE) && s->pb)
-- 
2.16.4