asivery via ffmpeg-devel:
> +typedef struct {
> + int block_count;
> +} AeaMuxerContext;
> +
> +static int aea_init(AVFormatContext *s)
> +{
> + AeaMuxerContext *c = s->priv_data;
> + c->block_count = 0;
Unnecessary: A muxer's priv_data is always pre-zeroed.
> +
> + return 0;
> +}
> +
> +static int aea_write_header(AVFormatContext *s)
> +{
> + AVDictionaryEntry *title_entry;
const
> + int title_length = 0, i;
> + char* title_contents;
> + AVStream *st;
> +
> +
> + if (s->nb_streams > 1) {
> + av_log(s, AV_LOG_WARNING, "Got more than one stream to encode, they
> will be ignored.\n");
We don't ignore extraneous streams, we normally error out if something
like this happens.
> + }
> +
> + st = s->streams[0];
> + if (st->codecpar->ch_layout.nb_channels != 1 &&
> st->codecpar->ch_layout.nb_channels != 2) {
> + av_log(s, AV_LOG_ERROR, "Invalid amount of channels to mux (%d).\n",
> st->codecpar->ch_layout.nb_channels);
> + return AVERROR(EINVAL);
> + }
> +
> + if (st->codecpar->sample_rate != 44100) {
> + av_log(s, AV_LOG_ERROR, "Invalid sample rate (%d) AEA only supports
> 44.1kHz.\n", st->codecpar->sample_rate);
> + return AVERROR(EINVAL);
> + }
> +
> + /* Write magic */
> + avio_wl32(s->pb, 2048);
> +
> + /* Write AEA title */
> + title_entry = av_dict_get(st->metadata, "title", NULL, 0);
> + if (title_entry) {
> + title_contents = title_entry->value;
> + title_length = FFMIN(256, strlen(title_contents));
Don't use strlen() in FFMIN (like many macros, it can evaluate its
argument multiple times).
> + }
> +
> + if (title_length) {
> + avio_write(s->pb, title_contents, title_length);
> + }
No need for this branch, just call this inside the "if (title_entry)"
block above.
> +
> + for (i = 0; i<(256 - title_length); i++) {
> + avio_w8(s->pb, 0);
> + }
ffio_fill(). Same below.
> +
> + /* Write number of frames (zero at header-writing time, will seek
> later), number of channels */
> + avio_wl32(s->pb, 0);
> + avio_w8(s->pb, st->codecpar->ch_layout.nb_channels);
> + avio_w8(s->pb, 0);
> +
> + /* Write flags (meaning unknown) */
> + for(i = 0; i<11; i++) {
> + avio_wl32(s->pb, 0);
> + }
> +
> + /* Pad the header to 2048 bytes */
> + for(i = 0; i<1738; i++) avio_w8(s->pb, 0);
> +
> + return 0;
> +}
> +
> +static int aea_write_packet(struct AVFormatContext *s, AVPacket *pkt)
> +{
> + AeaMuxerContext *c = s->priv_data;
> + c->block_count++;
> +
> + avio_write(s->pb, pkt->data, pkt->size);
> + return 0;
You can avoid this and the whole muxer context by using
ff_raw_write_packet() and relying on AVStream.nb_frames.
> +}
> +
> +static int aea_write_trailer(struct AVFormatContext *s)
> +{
> + AVIOContext *pb = s->pb;
> + AeaMuxerContext *c = s->priv_data;
> + if (pb->seekable & AVIO_SEEKABLE_NORMAL) {
> + /* Seek to rewrite the block count. */
> + avio_seek(pb, 260, SEEK_SET);
> + avio_wl32(pb, c->block_count *
> s->streams[0]->codecpar->ch_layout.nb_channels);
> + } else {
> + av_log(s, AV_LOG_WARNING, "unable to rewrite AEA header.\n");
> + }
> +
> + return 0;
> +}
> +
> +const FFOutputFormat ff_aea_muxer = {
> + .p.name = "aea",
> + .p.long_name = NULL_IF_CONFIG_SMALL("MD STUDIO audio"),
> + .priv_data_size = sizeof(AeaMuxerContext),
> + .p.extensions = "aea",
> + .p.audio_codec = AV_CODEC_ID_ATRAC1,
> + .init = aea_init,
> +
> + .write_header = aea_write_header,
> + .write_packet = aea_write_packet,
> + .write_trailer = aea_write_trailer,
> + .p.flags = AVFMT_GENERIC_INDEX,
Makes no sense for a muxer.
> +};
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