On 24/04/2025 01:10, James Almer wrote:
> On 4/23/2025 5:45 PM, Mark Thompson wrote:
>> +static int apv_read_header(AVFormatContext *s)
>> +{
>> + AVStream *st;
>> + GetByteContext gbc;
>> + APVHeaderInfo header;
>> + uint8_t buffer[28];
>> + uint32_t au_size, signature, pbu_size;
>> + int err, size;
>> +
>> + err = ffio_ensure_seekback(s->pb, sizeof(buffer));
>
> Isn't 28 bytes small enough that a backwards avio_seek() should always
> succeed?
I don't see any documentation to that effect and I'm not familiar with the
details of the implementation.
There are various calls in other places in lavf which give single-digit numbers
to ffio_ensure_seekback, so I'll keep it unless there is a guarantee somewhere
that I've missed.
>> + if (err < 0)
>> + return err;
>> + size = avio_read(s->pb, buffer, sizeof(buffer));
>> + if (size < 0)
>> + return size;
>> +
>> + bytestream2_init(&gbc, buffer, sizeof(buffer));
>> +
>> + au_size = bytestream2_get_be32(&gbc);
>> + if (au_size < 24) {
>> + // Too small.
>> + return AVERROR_INVALIDDATA;
>> + }
>> + signature = bytestream2_get_be32(&gbc);
>> + if (signature != APV_SIGNATURE) {
>> + // Signature is mandatory.
>> + return AVERROR_INVALIDDATA;
>> + }
>> + pbu_size = bytestream2_get_be32(&gbc);
>> + if (pbu_size < 16) {
>> + // Too small.
>> + return AVERROR_INVALIDDATA;
>> + }
>> +
>> + err = apv_extract_header_info(&header, &gbc);
>> + if (err < 0)
>> + return err;
>> +
>> + st = avformat_new_stream(s, NULL);
>> + if (!st)
>> + return AVERROR(ENOMEM);
>> +
>> + st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
>> + st->codecpar->codec_id = AV_CODEC_ID_APV;
>> + st->codecpar->format = header.pixel_format;
>> + st->codecpar->profile = header.profile_idc;
>> + st->codecpar->level = header.level_idc;
>> + st->codecpar->width = header.frame_width;
>> + st->codecpar->height = header.frame_height;
>> +
>> + st->avg_frame_rate = (AVRational){ 30, 1 };
>> + avpriv_set_pts_info(st, 64, 1, 30);
>> +
>> + avio_seek(s->pb, -size, SEEK_CUR);
>> +
>> + return 0;
>> +}
>> +
>> +static int apv_read_packet(AVFormatContext *s, AVPacket *pkt)
>> +{
>> + uint32_t au_size;
>> + int ret;
>> +
>> + au_size = avio_rb32(s->pb);
>> + if (au_size == 0 && avio_feof(s->pb))
>> + return AVERROR_EOF;
>> + if (au_size < 16 || au_size > 1 << 24) {
>
> Might be a good idea to also check for the signature.
Fair, added.
Also made the upper limit a bit bigger because it feels a little too close if
16K video is ever a thing.
>> + av_log(s, AV_LOG_ERROR, "APV AU is bad\n");
>> + return AVERROR_INVALIDDATA;
>> + }
>> +
>> + ret = av_get_packet(s->pb, pkt, au_size);
>> + pkt->flags = AV_PKT_FLAG_KEY;
>> +
>> + return ret;
>> +}
Thanks,
- Mark
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