Am Fr., 11. Sept. 2020 um 08:36 Uhr schrieb Josef Zlomek <jo...@pex.com>:
This is not the requested review, I am just curious about the
behaviour:
> +static int webp_probe(const AVProbeData *p)
> +{
> + const uint8_t *b = p->buf;
> +
> + if (AV_RB32(b) == MKBETAG('R', 'I', 'F', 'F') &&
> + AV_RB32(b + 8) == MKBETAG('W', 'E', 'B', 'P'))
> + return AVPROBE_SCORE_MAX;
What happens if you pipe several (not animated) webp images
through your new demuxer?
Does it behave like the existing pipe demuxer?
> +static int ensure_seekback(AVFormatContext *s, int64_t bytes)
> +{
> + WebPDemuxContext *wdc = s->priv_data;
> + AVIOContext *pb = s->pb;
> + int ret;
> +
> + int64_t pos = avio_tell(pb);
> + if (pos < 0)
> + return pos;
> +
> + if (pos + bytes <= wdc->seekback_buffer_end)
> + return 0;
> +
> + if ((ret = ffio_ensure_seekback(pb, bytes)) < 0)
> + return ret;
> +
> + wdc->seekback_buffer_end = pos + bytes;
> + return 0;
> +}
> +
> +static int resync(AVFormatContext *s, int seek_to_start)
> +{
> + WebPDemuxContext *wdc = s->priv_data;
> + AVIOContext *pb = s->pb;
> + int ret;
> + int i;
> + uint64_t state = 0;
> +
> + // ensure seek back for the file header and the first chunk header
> + if ((ret = ensure_seekback(s, 12 + 8)) < 0)
> + return ret;
> +
> + for (i = 0; i < 12; i++) {
> + state = (state << 8) | avio_r8(pb);
> + if (i == 11) {
> + if ((uint32_t) state == MKBETAG('W', 'E', 'B', 'P'))
The cast looks really ugly: Why is it necessary?
Carl Eugen
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