[FFmpeg-devel] [PATCH] avcodec/libmp3lame: check channel count after the lame_init_params()
James Almer
jamrial at gmail.com
Fri Jan 14 16:28:34 EET 2022
LAME will silently change the channel count value if you pass it an unsupported
one.
This should normally not be an issue as we ensure only 1 and 2 channel streams
are ever initialized, but since LAME could make changes outside our control
anytime, add an extra check for this.
Signed-off-by: James Almer <jamrial at gmail.com>
---
A crash can be triggered if you remove the AVCodec.channel_layouts array, in
which case non-mono and non-stereo streams will be initialized, but LAME will
try to encode them as if they were stereo.
I decided to not make this an assert() since, like i said above and even if
unlikely to happen, LAME could make changes and suddenly the list of valid
layouts we defined is no longer correct.
libavcodec/libmp3lame.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/libavcodec/libmp3lame.c b/libavcodec/libmp3lame.c
index 5675864bb2..93d2ef348a 100644
--- a/libavcodec/libmp3lame.c
+++ b/libavcodec/libmp3lame.c
@@ -142,6 +142,15 @@ static av_cold int mp3lame_encode_init(AVCodecContext *avctx)
goto error;
}
+ /* LAME does not error out on unsupported channel values and silently
+ * changes it to a supported one. Look for this and abort.
+ */
+ if (lame_get_num_channels(s->gfp) != avctx->channels) {
+ av_log(avctx, AV_LOG_ERROR, "Incosistent channel count\n");
+ ret = AVERROR_EXTERNAL;
+ goto error;
+ }
+
/* get encoder delay */
avctx->initial_padding = lame_get_encoder_delay(s->gfp) + 528 + 1;
ff_af_queue_init(avctx, &s->afq);
--
2.34.1
More information about the ffmpeg-devel
mailing list