[Ffmpeg-devel] [PATCH] apple caff demuxer
Baptiste Coudurier
baptiste.coudurier
Sun Apr 1 14:36:15 CEST 2007
Hi
Justin Ruggles wrote:
> Hi,
>
> Here is a demuxer for Apple CAFF files. It was written using
> documentation from:
> http://developer.apple.com/reference/MusicAudio/idxCoreAudio-date.html
>
> I basically wrote it because I needed to learn more about
> libavformat...and I think CAFF has a fairly good design.
>
> The demuxer reuses uses a function from mov.c, which I moved to isom.c/h.
>
> Currently I only have samples for pcm and aac, so those are the only
> codecs which are enabled. I need to have samples because the
> documentation only covers the 'kuki' chunk layout for AAC. The layout
> of that chunk is needed for each codec in order to get the proper
> extradata. I imagine many of the other codecs have a similar format
> (mp4 esds atom), but I don't want to assume anything at this point.
>
> I can upload samples to mplayerhq if/when I get permission from the
> person who sent them to me. It would also be great if anyone else has
> samples or can generate samples containing other codecs.
>
> I'll eventually write a muxer as well, hence the splitting of the
> demuxer into caff.c and caffdec.c.
>
> +/*
> +known tags which are either not supported in FFmpeg or we do not have
> +samples in order to know what the 'kiki' chunk format is in relation to
> +the required extradata format in the decoder.
Why not adding them in caff_tags and commenting them out ?
> +
> +void ff_caff_get_codec_id(CaffContext *ctx)
> +{
> + ctx->codec_id = CODEC_ID_NONE;
> +
> + /* codec selection for lpcm is chosen using format description and flags */
> + if(ctx->format_id == MKBETAG('l','p','c','m')) {
> + /* unpacked 24-bit is not currently supported */
> + if((ctx->bits_per_channel == 24) &&
> + (ctx->bytes_per_packet == (ctx->channels_per_frame * 4))) {
> + return;
> + }
> + /* floating-point lpcm is not currently supported */
> + if(ctx->format_flags & CAFF_LPCM_FLAGS_IS_FLOAT) {
> + return;
> + }
> + if(ctx->bits_per_channel == 8) {
> + ctx->codec_id = CODEC_ID_PCM_S8;
> + } else if(ctx->bits_per_channel == 16) {
> + if(ctx->format_flags & CAFF_LPCM_FLAGS_IS_LITTLEENDIAN) {
> + ctx->codec_id = CODEC_ID_PCM_S16LE;
> + } else {
> + ctx->codec_id = CODEC_ID_PCM_S16BE;
> + }
> + } else if(ctx->bits_per_channel == 24) {
> + if(ctx->format_flags & CAFF_LPCM_FLAGS_IS_LITTLEENDIAN) {
> + ctx->codec_id = CODEC_ID_PCM_S24LE;
> + } else {
> + ctx->codec_id = CODEC_ID_PCM_S24BE;
> + }
> + } else if(ctx->bits_per_channel == 32) {
> + if(ctx->format_flags & CAFF_LPCM_FLAGS_IS_LITTLEENDIAN) {
> + ctx->codec_id = CODEC_ID_PCM_S32LE;
> + } else {
> + ctx->codec_id = CODEC_ID_PCM_S32BE;
> + }
that mess begins to be duplicated in every demuxer, maybe
CODEC_ID_RAWAUDIO should be added, how to handle the BE/LE case ?
> [...]
> +
> +typedef struct {
> + int codec_id; ///< libavcodec CODEC_ID_*
> +
> + double sample_rate; ///< sampling frequency
> + int format_id; ///< 4-byte codec tag
why duplicating them from codec ?
> [...]
> + int channels_per_frame; ///< number of channels
> + int bits_per_channel; ///< sample bit depth, e.g. 16-bit audio
same
> [...]
> +
> + if(ctx->codec_id == CODEC_ID_AAC) {
> + /* The magic cookie format for AAC is an mp4 esds atom.
> + The lavc aac decoder requires the data from the codec specific
> + description as extradata input. */
> +
> + int tag, strt, len, cid, obj;
> +
> + strt = url_ftell(pb);
> + tag = get_byte(pb);
> + len = ff_mov_mp4_read_descr_len(pb);
> + if(tag == 3)
> + url_fskip(pb, 3);
> + else
> + url_fskip(pb, 2);
> + if((url_ftell(pb) - strt) < size) {
> + tag = get_byte(pb);
> + len = ff_mov_mp4_read_descr_len(pb);
> + if(tag == 4) {
> + obj = get_byte(pb);
> + url_fskip(pb, 12);
> + cid = codec_get_id(ff_mp4_obj_type, obj);
> + if(cid != ctx->codec_id) {
> + av_log(s, AV_LOG_WARNING, "MP4 object type mismatch\n");
> + }
> + while((url_ftell(pb) - strt) < size) {
> + tag = get_byte(pb);
> + len = ff_mov_mp4_read_descr_len(pb);
> + if(tag == 5) {
> + codec->extradata = av_mallocz(len + FF_INPUT_BUFFER_PADDING_SIZE);
> + if(codec->extradata) {
> + get_buffer(pb, codec->extradata, len);
> + codec->extradata_size = len;
> + }
> + } else {
> + url_fskip(pb, len);
> + }
> + }
> + }
> + }
That code pretty much looks like mov_read_esds, move it to isom.c, adapt
it if needed.
> [...]
> + ctx->num_packets = get_be64(pb);
> + ctx->packet_table = av_mallocz(ctx->num_packets *
> + sizeof(PacketTableEntry));
check for overflow before mul.
> [...]
> +
> + memset(ctx, 0, sizeof(CaffContext));
useless.
> + /* audio description chunk */
> + if(get_be32(pb) != MKBETAG('d','e','s','c')) {
> + av_log(s, AV_LOG_ERROR, "desc chunk not present\n");
> + return AVERROR_INVALIDDATA;
> + }
> + size = get_be64(pb);
> + ret = caff_read_desc(s, size);
> + if(ret)
> + return ret;
> + st = s->streams[0];
> + codec = st->codec;
> +
> + /* parse each chunk */
> + found_data = 0;
> + while(!url_feof(pb)) {
> +
> + /* stop at data chunk if seeking is not supported or
> + data chunk size is unknown */
> + if(found_data && (ctx->data_size < 0 || !pb->seek))
> + break;
why not url_is_streamed() instead of pb->seek ?
> [...]
> + break;
> +
> + /* TODO: other documented chunks */
> + case MKBETAG('c','h','a','n'):
> + case MKBETAG('s','t','r','g'):
> + case MKBETAG('m','a','r','k'):
> + case MKBETAG('r','e','g','n'):
> + case MKBETAG('i','n','s','t'):
> + case MKBETAG('m','i','d','i'):
> + case MKBETAG('o','v','v','w'):
> + case MKBETAG('e','d','c','t'):
> + case MKBETAG('i','n','f','o'):
> + case MKBETAG('u','m','i','d'):
> + case MKBETAG('u','u','i','d'):
> + case MKBETAG('f','r','e','e'):
> + if(size < 0)
> + return AVERROR_INVALIDDATA;
> + url_fskip(pb, size);
> + break;
IMHO don't mention those useless atom for now, and add them when there
are parsed/needed.
> [...]
> +
> + av_set_pts_info(st, 64, 1, st->codec->sample_rate);
> + st->start_time = 0;
> + st->duration = st->nb_frames;
wrong, duration is in stream timebase according to demuxers and utils.c,
btw doxy is also wrong in avformat.h.
> + /* position the stream at the start of data */
> + if(ctx->data_size >= 0 && pb->seek)
> + url_fseek(pb, ctx->data_start, SEEK_SET);
same url_is_streamed.
> + return 0;
> +}
> +
> +#define MAX_SIZE 4096
> +
> +static int caff_read_packet(AVFormatContext *s, AVPacket *pkt)
> +{
> + ByteIOContext *pb = &s->pb;
> + CaffContext *ctx = (CaffContext *)s->priv_data;
useless cast and there are more before also, I missed them.
> [...]
> +
> + pkt->size = res;
> + pkt->stream_index = 0;
I missed it but caff only supports one track ?
> + ctx->packet_cnt += packets_read;
> + ctx->frame_cnt += pkt_frames * packets_read;
> +
> + return 0;
> +}
> +
> +static int caff_read_close(AVFormatContext *s)
> +{
> + if(s && s->priv_data) {
> + CaffContext *ctx = (CaffContext *)s->priv_data;
> + if(ctx->packet_table) {
> + av_freep(&ctx->packet_table);
> + }
> + av_freep(&ctx);
> + }
> + return 0;
> +}
useless check, and priv_data is freed in utils.c, when
av_close_input_file is called.
> +
> +static int caff_read_seek(AVFormatContext *s, int stream_index,
> + int64_t timestamp, int flags)
> +{
> + CaffContext *ctx = s->priv_data;
> + int64_t bpos;
> +
> + /* FIXME: simplify */
> + if(ctx->frames_per_packet > 0 && ctx->bytes_per_packet > 0) {
> + ctx->frame_cnt = FFMAX(ctx->frame_cnt+timestamp, 0);
> + bpos = ctx->bytes_per_packet * ctx->frame_cnt / ctx->frames_per_packet;
> + bpos = FFMIN(bpos, ctx->data_size);
> + ctx->packet_cnt = bpos / ctx->bytes_per_packet;
> + ctx->frame_cnt = ctx->frames_per_packet * ctx->packet_cnt;
> + url_fseek(&s->pb, bpos + ctx->data_start, SEEK_SET);
> + } else if(ctx->has_packet_table) {
> + ctx->frame_cnt = FFMAX(ctx->frame_cnt+timestamp, 0);
> + ctx->packet_cnt = ctx->frame_cnt / ctx->frames_per_packet;
> + ctx->frame_cnt = ctx->packet_cnt * ctx->frames_per_packet;
> + ctx->packet_cnt = FFMIN(ctx->packet_cnt, ctx->num_packets-1);
> + bpos = ctx->packet_table[ctx->packet_cnt].bpos;
> + ctx->frame_cnt = ctx->packet_table[ctx->packet_cnt].fpos;
> + bpos = FFMIN(bpos, ctx->data_size);
> + url_fseek(&s->pb, bpos + ctx->data_start, SEEK_SET);
> + return 0;
> + } else {
I need more time to review that.
Btw, changelog, avformat.h, doxy need update too.
[...]
--
Baptiste COUDURIER GnuPG Key Id: 0x5C1ABAAA
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