[FFmpeg-devel] [PATCH] MP4 Subtitle support
Clément Bœsch
ubitux at gmail.com
Thu Oct 4 09:47:16 CEST 2012
On Wed, Oct 03, 2012 at 04:29:53PM +0200, Benjamin Rainer wrote:
> modified: libavformat/isom.c
> modified: libavformat/isom.h
> modified: libavformat/mov.c
> modified: libavformat/riff.h
> modified: libavformat/utils.c
>
> Added support for subtitles in MP4 (other than tx3g). Added support for the TextMetadataSampleEntry box ('mett') and XMLMetadataSampleEntry box ('metx'). Codecs are detected by the mime type.
> ---
> libavformat/isom.c | 9 ++++++++
> libavformat/isom.h | 1 +
> libavformat/mov.c | 63 +++++++++++++++++++++++++++++++++++++++++++--------
> libavformat/riff.h | 1 +
> libavformat/utils.c | 13 +++++++++++
> 5 files changed, 77 insertions(+), 10 deletions(-)
>
> diff --git a/libavformat/isom.c b/libavformat/isom.c
> index caa4d17..1396c9e 100644
> --- a/libavformat/isom.c
> +++ b/libavformat/isom.c
> @@ -302,6 +302,15 @@ const AVCodecTag ff_codec_movsubtitle_tags[] = {
> { AV_CODEC_ID_NONE, 0 },
> };
>
> +const CodecMime ff_codec_movsubtitle_mimetypes[] = {
> + { "text/srt", AV_CODEC_ID_SRT }, /* extend */
> + { "text/subip", AV_CODEC_ID_SUBRIP },
> + { "text/webvtt", AV_CODEC_ID_WEBVTT },
> + { "text/rtext", AV_CODEC_ID_REALTEXT },
> + { "text/subV", AV_CODEC_ID_SUBVIEWER },
> + { "", AV_CODEC_ID_NONE },
> +};
Tabs are not allowed in FFmpeg. Also you ave a typo: s/subip/subrip/
> +
> /* map numeric codes from mdhd atom to ISO 639 */
> /* cf. QTFileFormat.pdf p253, qtff.pdf p205 */
> /* http://developer.apple.com/documentation/mac/Text/Text-368.html */
> diff --git a/libavformat/isom.h b/libavformat/isom.h
> index 370ba43..4a52a28 100644
> --- a/libavformat/isom.h
> +++ b/libavformat/isom.h
> @@ -33,6 +33,7 @@ extern const AVCodecTag ff_mp4_obj_type[];
> extern const AVCodecTag ff_codec_movvideo_tags[];
> extern const AVCodecTag ff_codec_movaudio_tags[];
> extern const AVCodecTag ff_codec_movsubtitle_tags[];
> +extern const CodecMime ff_codec_movsubtitlte_mime_types[];
>
> int ff_mov_iso639_to_lang(const char lang[4], int mp4);
> int ff_mov_lang_to_iso639(unsigned code, char to[4]);
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 0639ddb..129dcdf 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -394,6 +394,25 @@ static int mov_read_udta_string(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> return 0;
> }
>
> +static int mov_read_metadata_string(AVDictionary **metadata, AVIOContext *pb, MOVAtom atom, const char *dict_entry_name)
> +{
> + char *str,*p;
> +
> + p = str = (char *)av_mallocz(atom.size); /* we do not know the size of the string, size of the box should be enough */
> +
> + if(!str)
> + return AVERROR(ENOMEM);
> +
> + while((*str = avio_r8(pb)) != (int)NULL) str++;
> +
> + av_dict_set(metadata, dict_entry_name, p,0); /* add the string into our dictonary */
> +
typo: dictionary
You also have various trailing whitespaces.
> + av_free(p);
> +
> + return 0;
> +
> +}
> +
> static int mov_read_chpl(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> {
> int64_t start;
> @@ -563,7 +582,7 @@ static int mov_read_hdlr(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
> else if (type == MKTAG('m','1','a',' '))
> st->codec->codec_id = AV_CODEC_ID_MP2;
> - else if ((type == MKTAG('s','u','b','p')) || (type == MKTAG('c','l','c','p')))
> + else if ((type == MKTAG('s','u','b','p')) || (type == MKTAG('c','l','c','p')) || (type == MKTAG('s','u','b','m')) || (type == MKTAG('s','u','b','r')))
> st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
>
> avio_rb32(pb); /* component manufacture */
> @@ -1237,7 +1256,7 @@ int ff_mov_read_stsd_entries(MOVContext *c, AVIOContext *pb, int entries)
> }
> /* we cannot demux concatenated h264 streams because of different extradata */
> if (st->codec->codec_tag && st->codec->codec_tag == AV_RL32("avc1"))
> - av_log(c->fc, AV_LOG_WARNING, "Concatenated H.264 might not play corrently.\n");
> + av_log(c->fc, AV_LOG_WARNING, "Concatenated H.264 might not play correctly.\n");
> sc->pseudo_stream_id = st->codec->codec_tag ? -1 : pseudo_stream_id;
> sc->dref_id= dref_id;
>
> @@ -1455,14 +1474,38 @@ int ff_mov_read_stsd_entries(MOVContext *c, AVIOContext *pb, int entries)
> sc->sample_size = (bits_per_sample >> 3) * st->codec->channels;
> }
> } else if (st->codec->codec_type==AVMEDIA_TYPE_SUBTITLE){
> - // ttxt stsd contains display flags, justification, background
> - // color, fonts, and default styles, so fake an atom to read it
> - MOVAtom fake_atom = { .size = size - (avio_tell(pb) - start_pos) };
> - if (format != AV_RL32("mp4s")) // mp4s contains a regular esds atom
> - mov_read_glbl(c, pb, fake_atom);
> - st->codec->codec_id= id;
> - st->codec->width = sc->width;
> - st->codec->height = sc->height;
> + /* if we got the mett box there has to be the mime_format set, so we can select the appropriate codec for subtitles*/
> + if(format == MKTAG('m','e','t','t'))
> + {
> + MOVAtom mett_atom = { .size = size - (avio_tell(pb) - start_pos) };
> +
> + mov_read_metadata_string(&st->metadata, pb, mett_atom, "content_encoding"); /* optional */
> + mov_read_metadata_string(&st->metadata, pb, mett_atom, "mime_format");
> +
> + st->codec->codec_id = ff_codec_get_id_from_mime(ff_codec_movsubtitle_mimetypes, ((AVDictionaryEntry *)av_dict_get(st->metadata, "mime_format", NULL, 0))->value);
> +
> + }else if(format == MKTAG('m','e','t','x'))
> + {
> + MOVAtom metx_atom = { .size = size - (avio_tell(pb) - start_pos) };
> +
> + mov_read_metadata_string(&st->metadata, pb, metx_atom, "content_encoding"); /* optional */
> + mov_read_metadata_string(&st->metadata, pb, metx_atom, "namespace");
> + mov_read_metadata_string(&st->metadata, pb, metx_atom, "schema_location"); /* optional */
> +
> + /* should identify codec by the namespace ... */
> +
> + }else
> + {
> +
> + // ttxt stsd contains display flags, justification, background
> + // color, fonts, and default styles, so fake an atom to read it
> + MOVAtom fake_atom = { .size = size - (avio_tell(pb) - start_pos) };
> + if (format != AV_RL32("mp4s")) // mp4s contains a regular esds atom
> + mov_read_glbl(c, pb, fake_atom);
> + st->codec->codec_id= id;
> + st->codec->width = sc->width;
> + st->codec->height = sc->height;
> + }
On the form: various typo, trailing whitespaces, tabs and bad styles;
please stick with the surrounding coding style.
BTW overall I think the approach is wrong: what you likely want is a "raw
text" subtitles encoder: basically a subtitle codec to strip all the ASS
tags from the internal representation, and use it in MOV to encode text
(with no markup) subtitles.
Why: because I believe putting various broken markups into MOV is wrong,
and it also means quite a maintenance burden to support all the different
subtitles codecs into MOV (and add some regularly).
[...]
--
Clément B.
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