[FFmpeg-devel] [PATCH] avformat/mov: (v4) fix get_eia608_packet

[Pavel Koshevoy]

On Wed, Feb 26, 2025 at 8:03 PM Zhao Zhili <
quinkblack-at-foxmail.com at ffmpeg.org> wrote:

>
>
> > On Feb 24, 2025, at 00:47, Pavel Koshevoy <pkoshevoy at gmail.com> wrote:
> >
> > On Fri, Feb 21, 2025 at 9:49 AM Pavel Koshevoy <pkoshevoy at gmail.com>
> wrote:
> >
> >> If there are no further constructive review comments today and tomorrow
> >> then I will commit and push this change on Sunday (if I don't forget).
> >>
> >> Pavel.
> >>
> >
> >
> > Pushed in commit 5021764413a138f340ba46a9b145215b7535ea83
>
> You should remove ‘(v4)’ before push.
>
>

That would have been good to know two weeks ago, but thank you.

Pavel




> >
> > Pavel.
> >
> >
> >
> >
> >>
> >> On Thu, Feb 13, 2025 at 2:22 PM Pavel Koshevoy <pkoshevoy at gmail.com>
> >> wrote:
> >>
> >>> The problem is reproducible with "Test for Quicktime 608 CC file.mov"
> >>> from https://samples.ffmpeg.org/MPEG2/subcc/
> >>>
> >>> ffmpeg -i "Test for Quicktime 608 CC file.mov" -map 0 -c copy -y
> >>> remuxed.mov
> >>>
> >>> Prior to the fix QuickTime Player playback of remuxed.mov would
> >>> render garbage text for "English CC" subtitles.
> >>> ---
> >>> libavformat/mov.c | 70 +++++++++++++++++++++++++++++++++++++++--------
> >>> 1 file changed, 59 insertions(+), 11 deletions(-)
> >>>
> >>> diff --git a/libavformat/mov.c b/libavformat/mov.c
> >>> index 85aef33b19..5a91ef5b8c 100644
> >>> --- a/libavformat/mov.c
> >>> +++ b/libavformat/mov.c
> >>> @@ -10788,25 +10788,73 @@ static int mov_change_extradata(AVStream *st,
> >>> AVPacket *pkt)
> >>>     return 0;
> >>> }
> >>>
> >>> -static int get_eia608_packet(AVIOContext *pb, AVPacket *pkt, int size)
> >>> +static int get_eia608_packet(AVIOContext *pb, AVPacket *pkt, int
> >>> src_size)
> >>> {
> >>> -    int new_size, ret;
> >>> +    /* We can't make assumptions about the structure of the payload,
> >>> +       because it may include multiple cdat and cdt2 samples. */
> >>> +    const uint32_t cdat = AV_RB32("cdat");
> >>> +    const uint32_t cdt2 = AV_RB32("cdt2");
> >>> +    int ret, out_size = 0;
> >>>
> >>> -    if (size <= 8)
> >>> +    /* a valid payload must have size, 4cc, and at least 1 byte pair:
> */
> >>> +    if (src_size < 10)
> >>>         return AVERROR_INVALIDDATA;
> >>> -    new_size = ((size - 8) / 2) * 3;
> >>> -    ret = av_new_packet(pkt, new_size);
> >>> +
> >>> +    /* avoid an int overflow: */
> >>> +    if ((src_size - 8) / 2 >= INT_MAX / 3)
> >>> +        return AVERROR_INVALIDDATA;
> >>> +
> >>> +    ret = av_new_packet(pkt, ((src_size - 8) / 2) * 3);
> >>>     if (ret < 0)
> >>>         return ret;
> >>>
> >>> -    avio_skip(pb, 8);
> >>> -    for (int j = 0; j < new_size; j += 3) {
> >>> -        pkt->data[j] = 0xFC;
> >>> -        pkt->data[j+1] = avio_r8(pb);
> >>> -        pkt->data[j+2] = avio_r8(pb);
> >>> +    /* parse and re-format the c608 payload in one pass. */
> >>> +    while (src_size >= 10) {
> >>> +        const uint32_t atom_size = avio_rb32(pb);
> >>> +        const uint32_t atom_type = avio_rb32(pb);
> >>> +        const uint32_t data_size = atom_size - 8;
> >>> +        const uint8_t cc_field =
> >>> +            atom_type == cdat ? 1 :
> >>> +            atom_type == cdt2 ? 2 :
> >>> +            0;
> >>> +
> >>> +        /* account for bytes consumed for atom size and type. */
> >>> +        src_size -= 8;
> >>> +
> >>> +        /* make sure the data size stays within the buffer
> boundaries. */
> >>> +        if (data_size < 2 || data_size > src_size) {
> >>> +            ret = AVERROR_INVALIDDATA;
> >>> +            break;
> >>> +        }
> >>> +
> >>> +        /* make sure the data size is consistent with N byte pairs. */
> >>> +        if (data_size % 2 != 0) {
> >>> +            ret = AVERROR_INVALIDDATA;
> >>> +            break;
> >>> +        }
> >>> +
> >>> +        if (!cc_field) {
> >>> +            /* neither cdat or cdt2 ... skip it */
> >>> +            avio_skip(pb, data_size);
> >>> +            src_size -= data_size;
> >>> +            continue;
> >>> +        }
> >>> +
> >>> +        for (int32_t i = 0; i < data_size; i += 2) {
> >>> +            pkt->data[out_size] = (0x1F << 3) | (1 << 2) | (cc_field -
> >>> 1);
> >>> +            pkt->data[out_size + 1] = avio_r8(pb);
> >>> +            pkt->data[out_size + 2] = avio_r8(pb);
> >>> +            out_size += 3;
> >>> +            src_size -= 2;
> >>> +        }
> >>>     }
> >>>
> >>> -    return 0;
> >>> +    if (src_size > 0)
> >>> +        /* skip any remaining unread portion of the input payload */
> >>> +        avio_skip(pb, src_size);
> >>> +
> >>> +    av_shrink_packet(pkt, out_size);
> >>> +    return ret;
> >>> }
> >>>
> >>> static int mov_finalize_packet(AVFormatContext *s, AVStream *st,
> >>> AVIndexEntry *sample,
> >>> --
> >>> 2.43.0
> >>>
> >>>
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