Hi On Tue, Dec 26, 2023 at 04:52:47PM +0100, Tomas Härdin wrote: >
[...]
> +
> +static int apc_write_header(AVFormatContext *s)
> +{
> + AVIOContext *pb = s->pb;
> + AVCodecParameters *par;
> + AVStream *st;
> +
> + if (s->nb_streams != 1) {
> + av_log(s, AV_LOG_ERROR, "Must have exactly one stream\n");
> + return AVERROR(EINVAL);
> + }
> +
> + st = s->streams[0];
> + par = st->codecpar;
> +
> + if (par->ch_layout.nb_channels <= 0 || par->ch_layout.nb_channels > 2) {
> + av_log(s, AV_LOG_ERROR, "Must be mono or stereo\n");
> + return AVERROR(EINVAL);
> + }
> +
> + if (par->extradata_size != 0 && par->extradata_size != 8) {
> + av_log(s, AV_LOG_ERROR,
> + "Must have exactly 0 or 8 bytes of extradata, got %i\n",
> + par->extradata_size);
> + return AVERROR(EINVAL);
> + }
> +
> + ffio_wfourcc(pb, "CRYO");
> + ffio_wfourcc(pb, "_APC");
> + ffio_wfourcc(pb, "1.20");
> + avio_wl32(pb, 0); // number or samples
please add to the comment "updated in apc_write_trailer()"
> + avio_wl32(pb, par->sample_rate);
> +
> + // write extradata if we have it (remuxing)
> + // else write dummy values and wait for AV_PKT_DATA_NEW_EXTRADATA
> (encoding)
> + if (par->extradata_size) {
> + avio_write(pb, par->extradata, par->extradata_size);
> + } else {
> + avio_wl64(pb, 0);
> + }
> +
> + avio_wl32(pb, par->ch_layout.nb_channels - 1);
> + avpriv_set_pts_info(st, 64, 1, par->sample_rate);
> + return 0;
> +}
> +
> +static int apc_write_packet(AVFormatContext *s, AVPacket *pkt)
> +{
> + size_t extradata_size = 0;
> + const uint8_t *extradata = av_packet_get_side_data(
> + pkt, AV_PKT_DATA_NEW_EXTRADATA, &extradata_size);
> +
> + if (extradata_size == 8) {
> + // we got predictors from encoder
> + // try to seek back end write them
> + int64_t pos = avio_tell(s->pb), err;
> + if ((err = avio_seek(s->pb, 20, SEEK_SET)) >= 0) {
> + avio_write(s->pb, extradata, extradata_size);
> + avio_seek(s->pb, pos, SEEK_SET);
> + } else {
> + av_log(s, AV_LOG_ERROR, "Got predictors from encoder but
> couldn't seek back to write them\n");
> + // fail since we should always be able to do this within the
> avio cache
> + // unless the encoder gave us predictors way too late for some
> reason
> + return err;
> + }
> + }
I think the encoder should buffer data or use 2 passes
if it needs future data. seeking back in the muxer is a bit odd.
if it becomes available always in teh first packet then maybe the
whole header could be written in the first packet
I would suggest, you add APC support to nut.
Thats a good test to ensure the packet and extradata is set at the right time
for a generic muxer
> +
> + avio_write(s->pb, pkt->data, pkt->size);
> + return 0;
> +}
> +
> +static int apc_write_trailer(AVFormatContext *s)
> +{
> + int64_t file_size = avio_tell(s->pb);
> +
> + // write length, if we're able to seek back
> + if (avio_seek(s->pb, 12, SEEK_SET) >= 0) {
> + if (file_size - APC_HEADER_SIZE >
> + UINT32_MAX * s->streams[0]->codecpar->ch_layout.nb_channels
> / 2) {
> + av_log(s, AV_LOG_ERROR, "File too large\n");
> + return AVERROR(EINVAL);
> + }
> +
> + avio_wl32(s->pb, (file_size - APC_HEADER_SIZE) *
> + 2 /
> s->streams[0]->codecpar->ch_layout.nb_channels);
I think something like this is slightly cleaner:
int64_t number_of_samples = (file_size - APC_HEADER_SIZE) *
2 / s->streams[0]->codecpar->ch_layout.nb_channels;
if (number_of_samples > UINT32_MAX)
...
[...]
thx
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Avoid a single point of failure, be that a person or equipment.
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