[FFmpeg-devel] [PATCH v4 1/2] lavf/mpegenc: fix ever-growing fifo size since the new API

[Nicolas Gaullier]

The older av_fifo_realloc2 implemented an auto grow that
should be ported as such in the new API.

This patch introduces a limitation in the fifo buffer size.
The default is set to 128MB and may be overriden by a new user option.
The amount of memory allocated depends on multiple factors, including
the number of audio streams.
A worst case scenario is where an out-of-spec high video bitrate is
combined with numerous low bitrate audios.

A fatal error mentions the availability of fifo_size_limit option.

Fix regressing since ea511196a6c85eb433e10cdbecb0b2c722faf20d

Signed-off-by: Nicolas Gaullier <nicolas.gaullier at cji.paris>
---
 libavformat/mpegenc.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/libavformat/mpegenc.c b/libavformat/mpegenc.c
index cc47a43288..e0955a7d33 100644
--- a/libavformat/mpegenc.c
+++ b/libavformat/mpegenc.c
@@ -84,6 +84,7 @@ typedef struct MpegMuxContext {
     int64_t vcd_padding_bytes_written;
 
     int preload;
+    int fifo_size_limit;
 } MpegMuxContext;
 
 extern const AVOutputFormat ff_mpeg1vcd_muxer;
@@ -461,9 +462,10 @@ static av_cold int mpeg_mux_init(AVFormatContext *ctx)
                    av_get_media_type_string(st->codecpar->codec_type), i);
             return AVERROR(EINVAL);
         }
-        stream->fifo = av_fifo_alloc2(16, 1, 0);
+        stream->fifo = av_fifo_alloc2(16, 1, AV_FIFO_FLAG_AUTO_GROW);
         if (!stream->fifo)
             return AVERROR(ENOMEM);
+        av_fifo_auto_grow_limit(stream->fifo, s->fifo_size_limit);
     }
     bitrate       = 0;
     audio_bitrate = 0;
@@ -1207,10 +1209,6 @@ static int mpeg_mux_write_packet(AVFormatContext *ctx, AVPacket *pkt)
     pkt_desc->unwritten_size =
     pkt_desc->size           = size;
 
-    ret = av_fifo_grow2(stream->fifo, size);
-    if (ret < 0)
-        return ret;
-
     if (s->is_dvd) {
         // min VOBU length 0.4 seconds (mpucoder)
         if (is_iframe &&
@@ -1222,10 +1220,15 @@ static int mpeg_mux_write_packet(AVFormatContext *ctx, AVPacket *pkt)
         }
     }
 
-    av_fifo_write(stream->fifo, buf, size);
+    ret = av_fifo_write(stream->fifo, buf, size);
+    if (ret == AVERROR(ENOSPC))
+        av_log(s, AV_LOG_FATAL, "Input stream buffer overrun. "
+                "To avoid, increase fifo_size_limit option.\n");
+    if (ret < 0)
+        return ret;
 
     for (;;) {
-        int ret = output_packet(ctx, 0);
+        ret = output_packet(ctx, 0);
         if (ret <= 0)
             return ret;
     }
@@ -1277,6 +1280,7 @@ static void mpeg_mux_deinit(AVFormatContext *ctx)
 static const AVOption options[] = {
     { "muxrate", NULL,                                          OFFSET(user_mux_rate), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, ((1<<22) - 1) * (8 * 50), E },
     { "preload", "Initial demux-decode delay in microseconds.", OFFSET(preload),  AV_OPT_TYPE_INT, { .i64 = 500000 }, 0, INT_MAX, E },
+    { "fifo_size_limit", "Maximum allowed memory for buffering an input stream in bytes", OFFSET(fifo_size_limit), AV_OPT_TYPE_INT, {.i64 = 128 * 1024 * 1024 }, 16, FFMIN(INT_MAX, SIZE_MAX), E},
     { NULL },
 };
 
-- 
2.34.0