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avformat/mp3dec: avoid seek back and forth

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avio_seek() is called inside check(). Seeking to 'off' then seeking
to 'off + i' is unefficient, and it can loop 64 * 1024 times in the
worst case. When probe a malformed file over HTTP, it looks like
stucked forvever. ffio_ensure_seekback() doesn't solve the issue
when the stream is seekable but slow.

Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
This commit is contained in:
Zhao Zhili 2022-09-25 12:28:40 +08:00
parent 2205ccd216
commit 0d17f5228f
1 changed files with 8 additions and 10 deletions
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18
libavformat/mp3dec.c
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@ -408,18 +408,11 @@ static int mp3_read_header(AVFormatContext *s)
ffio_ensure_seekback(s->pb, i + 1024 + 4); ffio_ensure_seekback(s->pb, i + 1024 + 4);
frame_size = check(s->pb, off + i, &header); frame_size = check(s->pb, off + i, &header);
if (frame_size > 0) { if (frame_size > 0) {
ret = avio_seek(s->pb, off, SEEK_SET);
if (ret < 0)
return ret;
ffio_ensure_seekback(s->pb, i + 1024 + frame_size + 4); ffio_ensure_seekback(s->pb, i + 1024 + frame_size + 4);
ret = check(s->pb, off + i + frame_size, &header2); ret = check(s->pb, off + i + frame_size, &header2);
if (ret >= 0 && if (ret >= 0 &&
(header & MP3_MASK) == (header2 & MP3_MASK)) (header & MP3_MASK) == (header2 & MP3_MASK))
{ {
av_log(s, i > 0 ? AV_LOG_INFO : AV_LOG_VERBOSE, "Skipping %d bytes of junk at %"PRId64".\n", i, off);
ret = avio_seek(s->pb, off + i, SEEK_SET);
if (ret < 0)
return ret;
break; break;
} else if (ret == CHECK_SEEK_FAILED) { } else if (ret == CHECK_SEEK_FAILED) {
av_log(s, AV_LOG_ERROR, "Invalid frame size (%d): Could not seek to %"PRId64".\n", frame_size, off + i + frame_size); av_log(s, AV_LOG_ERROR, "Invalid frame size (%d): Could not seek to %"PRId64".\n", frame_size, off + i + frame_size);
@ -429,10 +422,15 @@ static int mp3_read_header(AVFormatContext *s)
av_log(s, AV_LOG_ERROR, "Failed to read frame size: Could not seek to %"PRId64".\n", (int64_t) (i + 1024 + frame_size + 4)); av_log(s, AV_LOG_ERROR, "Failed to read frame size: Could not seek to %"PRId64".\n", (int64_t) (i + 1024 + frame_size + 4));
return AVERROR(EINVAL); return AVERROR(EINVAL);
} }
ret = avio_seek(s->pb, off, SEEK_SET);
if (ret < 0)
return ret;
} }
if (i == 64 * 1024) {
ret = avio_seek(s->pb, off, SEEK_SET);
} else {
av_log(s, i > 0 ? AV_LOG_INFO : AV_LOG_VERBOSE, "Skipping %d bytes of junk at %"PRId64".\n", i, off);
ret = avio_seek(s->pb, off + i, SEEK_SET);
}
if (ret < 0)
return ret;
off = avio_tell(s->pb); off = avio_tell(s->pb);
// the seek index is relative to the end of the xing vbr headers // the seek index is relative to the end of the xing vbr headers