mp4 files embedding DVD subtitles do not use the same extradata format as the rest of Libav expects. The subtitle decoder in libavcodec in particular does not understand this format.
Convert the extradata to the vobsub .idx format. mp4 stores the palette as binary 32 bit ints in YUV. The subtitle resolution is stored separately in the track header, which we access through AVStream. --- Some uncertainties: - not sure if I got the component order right, and all samples I found had gray subs - should this write a header? Like: # VobSub index file, v7 (do not modify this line!) - is the width/height necessarily known at this point? the size comes from the "tkhd" element, and it looks like in theory it doesn't need to come before the other elements. Also, I tried to use libavutil/colorspace.h for the colorspace conversion. But it's so messy, and ff_cropTbl (needed for using it comfortably) is private to libavcodec. So I just copied the YUV to RGB conversion from some site. --- libavformat/isom.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) diff --git a/libavformat/isom.c b/libavformat/isom.c index b3f3f95..e13f9cf 100644 --- a/libavformat/isom.c +++ b/libavformat/isom.c @@ -26,6 +26,7 @@ #include "isom.h" #include "libavcodec/mpeg4audio.h" #include "libavcodec/mpegaudiodata.h" +#include "libavutil/intreadwrite.h" /* http://www.mp4ra.org */ /* ordered by muxing preference */ @@ -419,8 +420,60 @@ static const AVCodecTag mp4_audio_types[] = { { AV_CODEC_ID_NONE, AOT_NULL }, }; +static uint32_t yuv_to_rgba(uint32_t ycbcr) +{ + uint8_t r, g, b; + int y, cb, cr; + + y = (ycbcr >> 16) & 0xFF; + cr = (ycbcr >> 8) & 0xFF; + cb = ycbcr & 0xFF; + + b = av_clip_uint8(1.164 * (y - 16) + 2.018 * (cb - 128)); + g = av_clip_uint8(1.164 * (y - 16) - 0.813 * (cr - 128) - 0.391 * (cb - 128)); + r = av_clip_uint8(1.164 * (y - 16) + 1.596 * (cr - 128)); + + return (r << 16) | (g << 8) | b; +} + +static int mov_rewrite_dvd_sub_extradata(AVStream *st) +{ + char pal_s[256]; + char buf[256]; + int pal_s_pos = 0; + uint8_t *src = st->codec->extradata; + + if (st->codec->extradata_size != 64) + return 0; + + for (int i = 0; i < 16; i++) { + uint32_t yuv = AV_RB32(src + i * 4); + uint32_t rgba = yuv_to_rgba(yuv); + + snprintf(pal_s + pal_s_pos, sizeof(pal_s) - pal_s_pos, "%06x%s", rgba, + i != 15 ? ", " : ""); + pal_s_pos = strlen(pal_s); + if (pal_s_pos >= sizeof(pal_s)) + return 0; + } + + snprintf(buf, sizeof(buf), "size: %dx%d\npalette: %s\n", + st->codec->width, st->codec->height, pal_s); + + av_freep(&st->codec->extradata); + st->codec->extradata_size = 0; + st->codec->extradata = av_mallocz(strlen(buf) + FF_INPUT_BUFFER_PADDING_SIZE); + if (!st->codec->extradata) + return AVERROR(ENOMEM); + st->codec->extradata_size = strlen(buf); + memcpy(st->codec->extradata, buf, st->codec->extradata_size); + + return 0; +} + int ff_mp4_read_dec_config_descr(AVFormatContext *fc, AVStream *st, AVIOContext *pb) { + int err; int len, tag; int object_type_id = avio_r8(pb); avio_r8(pb); /* stream type */ @@ -460,6 +513,10 @@ int ff_mp4_read_dec_config_descr(AVFormatContext *fc, AVStream *st, AVIOContext cfg.object_type))) st->codec->codec_id = AV_CODEC_ID_AAC; } + if (st->codec->codec_id == AV_CODEC_ID_DVD_SUBTITLE) { + if ((err = mov_rewrite_dvd_sub_extradata(st)) < 0) + return err; + } } return 0; } -- 1.9.0 _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
