Quoting David Bryant (2020-04-06 06:56:05)
> On 4/5/20 1:32 PM, Anton Khirnov wrote:
> > They are not forbidden by the specification.
> > ---
> > libavformat/wvdec.c | 18 ------------------
> > 1 file changed, 18 deletions(-)
> >
> > diff --git a/libavformat/wvdec.c b/libavformat/wvdec.c
> > index b9fc6a59f9..4159bf1253 100644
> > --- a/libavformat/wvdec.c
> > +++ b/libavformat/wvdec.c
> > @@ -208,24 +208,6 @@ static int wv_read_block_header(AVFormatContext *ctx,
> > AVIOContext *pb)
> > if (!wc->rate)
> > wc->rate = rate * rate_x;
> >
> > - if (flags && bpp != wc->bpp) {
> > - av_log(ctx, AV_LOG_ERROR,
> > - "Bits per sample differ, this block: %i, header block:
> > %i\n",
> > - bpp, wc->bpp);
> > - return AVERROR_INVALIDDATA;
> > - }
> > - if (flags && !wc->multichannel && chan != wc->chan) {
> > - av_log(ctx, AV_LOG_ERROR,
> > - "Channels differ, this block: %i, header block: %i\n",
> > - chan, wc->chan);
> > - return AVERROR_INVALIDDATA;
> > - }
> > - if (flags && rate != -1 && !(flags & WV_DSD) && rate * rate_x !=
> > wc->rate) {
> > - av_log(ctx, AV_LOG_ERROR,
> > - "Sampling rate differ, this block: %i, header block: %i\n",
> > - rate * rate_x, wc->rate);
> > - return AVERROR_INVALIDDATA;
> > - }
> > return 0;
> > }
> >
>
> The specification does not explicitly mention that the data format, the
> channel count (and layout), and the sample rate cannot
> change inside of a WavPack file, but they can't. The first block of a WavPack
> file that contains audio determines the format of
> the entire file, and the documentation will be updated shortly to reflect
> that. And obviously Konstantin Shishkov was aware of
> this, even referring to the first block containing audio as the "header
> block".
>
> I have no issue with the decoder handling these changes as it might be
> receiving a WavPack stream from a container that allows
> this, but the native WavPack container doesn't. And I actually don't have any
> problem with this specific change going in because
> it doesn't actually break anything. However, it should not be possible to
> create a WavPack file with format changes such as these.
Okay, then maybe I'll drop this patch. My intent was for it to allow
adding tests for wavpack format changes, but I guess that can also be
done with matroska.
--
Anton Khirnov
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