| Message ID | 20240311140128.1730332-2-nicolas.gaullier@cji.paris |
|---|---|
| State | New |
| Headers | show |
| Series | avcodec/dolby_e: Add error recovery when parse_mantissas run out of bits | expand |
| Context | Check | Description |
|---|---|---|
| yinshiyou/make_loongarch64 | success | Make finished |
| yinshiyou/make_fate_loongarch64 | success | Make fate finished |
| andriy/make_x86 | success | Make finished |
| andriy/make_fate_x86 | success | Make fate finished |
>De : Nicolas Gaullier <nicolas.gaullier@cji.paris> >Envoyé : lundi 11 mars 2024 15:01 > >Mantissas are the last data in the channel subsegment and it appears it is sometimes missing a very few bits for the parsing to complete. >This must not be confused with data corruption. >In standard conditions with certified products, it has been observed that the occurence of this issue is pretty steady and about once every 2 hours. The truncation is at about 950 out of the 1024 values (923 is the minimum I have seen so far). >The current code raises a severe 'Read past end' error and all data is lost resulting in 20ms(@25fps) of silence for the affected channel. >This patch introduces a tolerance: if 800 out of the 1024 mantissas have been parsed, a simple warning is raised and the data is preserved. Ping ? still applies last posted here: https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=11090 Samples (source/before patch/after patch) here: https://0x0.st/oOvv.zip Nicolas
diff --git a/libavcodec/dolby_e.c b/libavcodec/dolby_e.c index 9c3f6006c2..1f8442e2e9 100644 --- a/libavcodec/dolby_e.c +++ b/libavcodec/dolby_e.c @@ -845,6 +845,7 @@ static int parse_indices(DBEContext *s, DBEChannel *c) return 0; } +#define MIN_MANTISSAS 800 static int parse_mantissas(DBEContext *s, DBEChannel *c) { DBEGroup *g; @@ -885,6 +886,13 @@ static int parse_mantissas(DBEContext *s, DBEChannel *c) } } } else { + if (i == c->nb_groups - 1 + && count * size1 > get_bits_left(&s->gb) + && get_bits_left(&s->gb) >= 0 + && (int)(mnt - c->mantissas) >= MIN_MANTISSAS) { + av_log(s->avctx, AV_LOG_WARNING, "Truncated mantissas @%d, highest frequencies not recoverable\n", (int)(mnt - c->mantissas)); + break; + } for (k = 0; k < count; k++) mnt[k] = get_sbits(&s->gb, size1) * scale; }
Mantissas are the last data in the channel subsegment and it appears it is sometimes missing a very few bits for the parsing to complete. This must not be confused with data corruption. In standard conditions with certified products, it has been observed that the occurence of this issue is pretty steady and about once every 2 hours. The truncation is at about 950 out of the 1024 values (923 is the minimum I have seen so far). The current code raises a severe 'Read past end' error and all data is lost resulting in 20ms(@25fps) of silence for the affected channel. This patch introduces a tolerance: if 800 out of the 1024 mantissas have been parsed, a simple warning is raised and the data is preserved. Signed-off-by: Nicolas Gaullier <nicolas.gaullier@cji.paris> --- libavcodec/dolby_e.c | 8 ++++++++ 1 file changed, 8 insertions(+)