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Commit 0b490550 authored by Hangyu Kuang's avatar Hangyu Kuang
Browse files

MPEG4Extractor: Read out the Metadata track correctly. 

The metadata track before API29 is not compliant with the standard. This
CL adds the support for reading out the mime_format correctly from compliant
and non-compliant metadata track.

Bug:  117950811
Test: CTS test.
Change-Id: I9a7033549962711b625f5a008a22930691ab3e5e
parent 6d34bed9

media/extractors/mp4/MPEG4Extractor.cpp

+33 −2
Original line number Diff line number Diff line
@@ -1556,9 +1556,40 @@ status_t MPEG4Extractor::parseChunk(off64_t *offset, int depth) { 
                return ERROR_IO;

            }



            String8 mimeFormat((const char *)(buffer.get()), chunk_data_size);

            AMediaFormat_setString(mLastTrack->meta, AMEDIAFORMAT_KEY_MIME, mimeFormat.string());

            // Prior to API 29, the metadata track was not compliant with ISO/IEC

            // 14496-12-2015. This led to some ISO-compliant parsers failing to read the

            // metatrack. As of API 29 and onwards, a change was made to metadata track to

            // make it compliant with the standard. The workaround is to write the

            // null-terminated mime_format string twice. This allows compliant parsers to

            // read the missing reserved, data_reference_index, and content_encoding fields

            // from the first mime_type string. The actual mime_format field would then be

            // read correctly from the second string. The non-compliant Android frameworks

            // from API 28 and earlier would still be able to read the mime_format correctly

            // as it would only read the first null-terminated mime_format string. To enable

            // reading metadata tracks generated from both the non-compliant and compliant

            // formats, a check needs to be done to see which format is used.

            int null_pos = 0;

            const unsigned char *str = buffer.get();

            while (null_pos < chunk_data_size) {

              if (*(str + null_pos) == '\0') {

                break;

              }

              ++null_pos;

            }



            if (null_pos == chunk_data_size - 1) {

              // This is not a standard ompliant metadata track.

              String8 mimeFormat((const char *)(buffer.get()), chunk_data_size);

              AMediaFormat_setString(mLastTrack->meta,

                  AMEDIAFORMAT_KEY_MIME, mimeFormat.string());

            } else {

              // This is a standard compliant metadata track.

              String8 contentEncoding((const char *)(buffer.get() + 8));

              String8 mimeFormat((const char *)(buffer.get() + 8 + contentEncoding.size() + 1),

                  chunk_data_size - 8 - contentEncoding.size() - 1);

              AMediaFormat_setString(mLastTrack->meta,

                  AMEDIAFORMAT_KEY_MIME, mimeFormat.string());

            }

            break;

        }